17 ms·

Efficient Air-Conditioning Beams Heat into Space

404 points by uoaei 9y ago

oomkiller 9y ago
I think the biggest question here is what saves more dirty energy. Obviously, these units will compete with solar for roof space. The sun beats down in the summer, where these panels would be most useful, but also where solar would hit peak power generation. As long as solar can supply at least 20% of the power required to cool the building, it seems like it will be a better option, as solar is also useful for other things like charging electric cars during the winter, when A/C is not required.
- jws 9y ago
  Even on a flat roof, there is room to add radiator panels without compromising solar space. The solar panels will be tipped up to the south some amount based on their latitude, but you don't want to shade the low end of a panel with the high end of the next one, so there is a gap between rows. A shaded gap. Precisely the best spot to put radiator panels. You could even imagine a combined product which would be a corrugated panel alternating "uphill" solar and "downhill" radiator segments with the dimensions tailored to the latitude. This could be installed flat on the roof.
  - dsr_ 9y ago
    180 degree flip panels. Solar cells during the day, IR radiators at night.
    - phinnaeus 9y ago
      Plus it would look super cool if you got them to flip in a wave pattern across your roof.
      - 0xfeba 9y ago
        I can see it now: malware communicating across air-gapped systems by way of flipping radiator panels on roofs.
        Micoloth 9y ago
        Yes this has to be it
        kerkeslager 9y ago
        After the CRISPR malware transmitted via actual genes, I'd barely be surprised.
        0xfeba 9y ago
        That was a lot of hype and not much else. They modified the machines that were reading the specially crafted DNA.
        nerpderp83 9y ago
        Life always finds a way.
  - politician 9y ago
    Tesla's SolarCity product consists of rooftop tiles, some of which are not solar panels -- approx. 50%. Those non-collecting panels could be replaced with IR emitting panels without much change to their overall strategy.
- DontGiveTwoFlux 9y ago
  This assumes it is most efficient to build the solar locally. These radiative panels have to be installed locally. Solar can be transmitted over wires from large scale plants.
hourislate 9y ago
Simply putting your outside AC Condenser Unit on the shady side of a house or have a Tree or Bush shade it can significantly reduce your energy usage. They units themselves are at least 20 Degrees cooler than being in direct sunlight. There are also misting units that use approx 1-2 gallons of water a day (equivalent to a toilet flush) that can also reduce energy consumption by up to 30%. Simple solutions for big savings.
- goda90 9y ago
  Swamp coolers are useless in high humidity climates. And similarly, shade isn't as cool relative to direct sunlight in high humidity either.
  - xenadu02 9y ago
    The water removes more heat from the coolant; the swamp cooler isn't for the inside of the house it's for the compressor itself.
- bmcusick 9y ago
  Your first claim was so interesting I had to Google it. But this article suggests it doesn't hold up. https://www.energyvanguard.com/blog/will-shading-your-air-conditioner-save-you-money https://www.energyvanguard.com/blog/will-shading-your-air-co... Moneyquote: "The temperature of the surrounding air has a much bigger effect on cooling efficiency than direct solar gain, and the volume of air pulled in by an air conditioner is huge."
  - hourislate 9y ago
    This article you are referring to is for a heat pump and so are the % of savings. An AC Condenser sitting in the Sunlight will naturally be a lot hotter in temperature than one sitting in the shade. For example park your car in the sunlight and then park your car in the shade? Where will the surface of your vehicle be hotter/cooler? It has nothing to do with air temperature at this point. It is the heat of the sunlight that is raising the temp of the coils in the condenser just like it would raise the temp of the surface of a vehicle parked in the sun instead of the shade. I live in TX. I have some experience with this.
vtange 9y ago
If this system is scalable area-wise wouldn't it be a good idea to shield the ice caps with this? A 3C to 5C degree difference could mean quite a bit in preventing further ice melting, no?
- kardos 9y ago
  The Arctic and Antarctic are very big. If you could somehow build a structure that would withstand the harsh conditions, I imagine using a mirror or even aluminum foil would be an overwhelmingly cheaper way of reflecting energy back out.
- goda90 9y ago
  I believe I saw a test where they put a white sheet over some ice in Greenland, and came back a year later. The ice under the sheet was multiple inches higher than the surrounding ice.
- jackhack 9y ago
  But that's just it -- it is NOT scaleable to any measure that would make a difference. The manufacturing effort alone would require quantities of raw material that would dwarf all construction efforts ever undertaken combined. There is the issue of mining, refining, manufacturing, transporation... not to mention the installation and maintenance of a hundred thousand square miles of reflective shields in an incredibly hostile (to life) environment. Even if the whole of humanity could agree this is the most pressing issue of civilization, we would wreck the earth to save the ice. It would be easier to build a shopping mall at the bottom of the ocean. And the sun will just get warmer anyway. It is folly to think we can play God. Climate change is normal, and natural. It has been happening since the beginning of time, and will continue long after all traces of life on Earth are gone. Who are we to attempt to interfere?
  - llukas 9y ago
    We already did play God by increasing CO2 in atmosphere. There is nothing wrong in efforts to mitigate its effect.
davidhyde 9y ago
A temperature drop of 3-5 degrees C is meaningless unless other variables are supplied. For example, how much water was cooled? They tell you how long (3 days) but they don't let you how many panels they used either. Too many 'science' articles these days don't add up.
- philipkglass 9y ago
  This is just a press release about the actual scientific publication. The abstract provides more information: https://www.nature.com/articles/nenergy2017143 https://www.nature.com/articles/nenergy2017143 Cooling systems consume 15% of electricity generated globally and account for 10% of global greenhouse gas emissions. With demand for cooling expected to grow tenfold by 2050, improving the efficiency of cooling systems is a critical part of the twenty-first-century energy challenge. Building upon recent demonstrations of daytime radiative sky cooling, here we demonstrate fluid cooling panels that harness radiative sky cooling to cool fluids below the air temperature with zero evaporative losses, and use almost no electricity. Over three days of testing, we show that the panels cool water up to 5 ∘C below the ambient air temperature at water flow rates of 0.2 l min−1 m−2, corresponding to an effective heat rejection flux of up to 70 W m−2. We further show through modelling that, when integrated on the condenser side of the cooling system of a two-storey office building in a hot dry climate (Las Vegas, USA), electricity consumption for cooling during the summer could be reduced by 21% (14.3 MWh). And you can read the full article via sci-hub to get all the experimental details.
  - kbenson 9y ago
    > the panels cool water up to 5 ∘C below the ambient air temperature at water flow rates of 0.2 l min−1 m−2, corresponding to an effective heat rejection flux of up to 70 W m−2. Can someone translate that into layman terms? The chained negative exponents are somewhat confusing. I would think 70 W m^2 would me square meters, but what's 70 W m^-2? I assume it's not really mappable to dimensions at that point...
    - ar813 9y ago
deleted 9y ago
[deleted]
Cshelton 9y ago
Wouldn't it be more efficient to just use water run through a coil 6 ft underground? In most areas that have the intense heat that running water over the radiators actually would help, the ground 6 ft below is pretty easily cooler than 5-10 degrees C. The electricity to pump 6 ft down couldn't be that much more either... And when it isn't as hot out, you can actually use the ground temp to radiate heat out of the house by itself, no need for coils and a fan to run in ambient air temp, right?
- fragsworth 9y ago
  Maybe digging is impractical in a lot of situations?
- renlo 9y ago
  The problem is that with ACs/power plants, the net temperature will rise if you do this because it's a closed system. Power plants and ACs are not 100% efficient; the power plant converts chemical/nuclear/mechanical energy into electrical energy, releasing heat from work lost. Your AC will convert electrical energy to cool the air around you, but because it is not 100% efficient, the total temperature of the system will rise. There needs to be a way to get rid of that lost energy and remove it from the system. If you put that into the ground, it's still in the system. Ofc, even when they try to 'beam the heat to space', much of it will end up staying in the system (earth) as it reflects on clouds / water vapor, etc.
  - Swizec 9y ago
    Isn’t this basically what happened with the London underground? It used to be cold down there now it’s super hot as the soil can’t absorb more heat. Source: https://www.forbes.com/forbes/welcome/?toURL=https://www.forbes.com/sites/lauriewinkless/2017/06/22/sweating-on-the-underground-why-are-tube-tunnels-so-hot/&refURL=https://www.google.com/&referrer=https://www.google.com/ https://www.forbes.com/forbes/welcome/?toURL=https://www.for... > According to this article in Rail Magazine, the average temperature inside the tunnels was around 14° in 1900. > increased the temperature of the surrounding clay so much that, today, average tunnel temperatures are between 20-25°C.
pavement 9y ago
into space Hmmm, that seems like a click-bait statement. Between the air conditioner and even low earth orbit, there's plenty of atmosphere that will soak up some of the beam's heat, no?
- mikeyouse 9y ago
  No offense, but did you read the article? It's directly addressed: > So Raman and electrical engineering professor Shanhui Fan made panels containing layers of silicon dioxide and hafnium oxide on top of a thin layer of silver. These radiate in a unique way: They send heat directly into space, bypassing the Earth’s atmosphere. The panels do this by emitting heat at infrared wavelengths between 8 and 13 micrometers. To these waves, the Earth’s atmosphere is transparent. What’s more, the panels reflect nearly all the sunlight falling on them. A little further research shows that the atmosphere is opaque at numerous wavelengths and it's probably safe to assume that they intentionally targeted the opaque ones: https://i.imgur.com/eUmTltm.png https://i.imgur.com/eUmTltm.png
  - iRobbery 9y ago
    While i understand you both. A title is a title. And the title claims 'heat' not reflecting infrared wavelengths between 8 and 13 micrometers. And imho 'heat' is more then certain ranges of infrared wavelengths. So in that sense i can see why somebody uses the word clickbait in regards to this title. edit joke While i'm just afraid the moon will start to condensate /edit
    - kbenson 9y ago
      It's removing heat from a system by radiating it into space. That it's radiated using infrared is irrelevant, since it does cool the system it is attached to. Even "beam" is appropriate in this instance. There's no "bait" in the "click-bait", it's exactly as advertised.
      - pavement 9y ago
        Listen, a little tl;dr is not too much to ask for around here, especially when the salient point is buried 7 paragraphs in, when it should be present in the leading sentence. Forgive me for not locating the relevant passage, while quickly skimming this and 100 other articles, while at work. Furthermore, regarding cloud cover, I am dubious of the premise that even the specified wavelengths penetrate otherwise opaque cloud cover. Sure, maybe that portion of the spectrum penetrates the typical atmospheric mix, including light water vapor, on an otherwise clear day, but, color me unsurprised if it fails to penetrate smog, diesel and particulate pollution, and other common dust constituents in cloud nuclei. I mean, even radar can be blinded by dense storm clouds. But hey, maybe I'm wrong, maybe it's a 100% miracle cure. Maybe it's that awesome. I hope I really am just a big dummy, too lazy to read a blurb more than three sentences long.
leggomylibro 9y ago
Huh - I'm always interested in ways to make A/C more energy efficient. Squeezing and un-squeezing gas seems so COMPLICATED compared to how easy it is to heat things up. Entropy is a cruel mistress. Anyways, it sounds like this is the important bit: - So Raman and electrical engineering professor Shanhui Fan made panels containing layers of silicon dioxide and hafnium oxide on top of a thin layer of silver. These radiate in a unique way: They send heat directly into space, bypassing the Earth’s atmosphere. The panels do this by emitting heat at infrared wavelengths between 8 and 13 micrometers. To these waves, the Earth’s atmosphere is transparent. What’s more, the panels reflect nearly all the sunlight falling on them. For the new fluid-cooling system, the researchers made radiative panels that were each one-third of a square meter in area; they attached the panels to an aluminum heat exchanger plate with copper pipes embedded in it. The setup was enclosed in an acrylic box covered with a plastic sheet. The team tested it on a rootop on the Stanford campus. Over three days of testing, they found that water temperatures went down by between 3- and 5 °C. The only electricity it requires is what’s needed to pump water through the copper pipes. Water that flowed more slowly was cooled more. - So it sounds like how space stations kick out heat; The ISS uses that sort of thing[1]. You flow coolant through things that heat up, like solar panels or a warm environment, and then you pump it into these bricks that don't absorb heat from light. The coolant warms up the bricks, which emit that heat as infrared radiation. Planetside, I guess that you can't let the infrared radiation be absorbed by the atmosphere, or it won't cool anything. So, maybe this could take the compression out of our current cooling systems - compress/heat up, expose to outside temp, let cool, decompress/cool, expose to inside temp, repeat. My main question would be, is it capable of cooling beyond the ambient outside temperature? If so, how? I might be misunderstanding or missing something about how the 'blasting energy away as IR radiation' thing works. [1]: http://www.lockheedmartin.com/us/products/HeatRejectionRadiators.html http://www.lockheedmartin.com/us/products/HeatRejectionRadia...
- ar813 9y ago
  I'm one of the authors / people working on this. Yep, radiators like the ones on the ISS are pretty much the dominant/only ways to get heat out in space. In response to your questions: yes, it can in fact cool below the ambient air temperature entirely passively (even during the day! -- which adds real value for cooling applications). We've shown in other recent work that you can use this effect to cool as much as 45-50°C below the ambient air temperature, if you insulate the radiator perfectly. The reason this works here on Earth is that some upward thermal radiation isn't absorbed and re-emitted back to you. So if you start at the air temperature, looking upwards, you will be sending more heat out than the sky sends back to you. This allows an upward-looking surface to cool itself down until the heat going out and coming back to it balance out.
ChuckMcM 9y ago
I am super excited they built a practical demonstration system out of this technology. I would love it if more 'breakthrough' research took it to this sort of proof of concept (I know it is hard to get funding for that sort of project but it is so useful). I would love to see self contained shade structures that would both shade and lightly cool the air underneath them.
jmh530 9y ago
How much does this save vs. replacing these panels with solar panels?
fpoling 9y ago
Atmosphere is only transparent for thermal infrared without clouds. Clouds emits and reflects ambient heat back to these panels heating them. But then one does not need typically air-conditioning on a cloudy day :)
- firebird84 9y ago
  Depends on where you live. :) Where I am, clouds do nothing.
  - lucb1e 9y ago
    Interesting! Do you know some examples of places where clouds influence temperature a lot and where it doesn't? And what causes this?
    - Roverlord 9y ago
      Maybe it's typical cloud base height?
seanalltogether 9y ago
If these become popular, maybe you could create a new solar panel that absorbs the wavelengths emitted by these air conditioners in order to create electricity ...or better yet...
- hwillis 9y ago
  These panels reject heat at a rate of up to 70 W/m^2. A good solar panel absorbs 20% of incoming light, which typically peaks at about 1000 W, so a solar panel reduces temperature by 3x as much. So... you could just do that.
  - irrelative 9y ago
    Furthermore, air conditioning isn't lowering the temperature of a system by the energy consumed. Rather, it acts like a heat pump which usually pumps more energy that is used. So 200 J/s of electric power running a typical AC unit would likely reject more than 200 J/s from a building.
- paddy_m 9y ago
  Could you create a solar panel that generates energy during the day and rejects heat during the night? Would it be efficient at either task?
- the8472 9y ago
  Solar panel efficiency decreases with rising temperatures, so maybe increasing its emissivity in the infrared window could improve efficiency.
swsieber 9y ago
Question - could one theoretically build a big enough array of this to counter-act globally warming? Any back of the envelope math for what it would take would be very interesting.
- hwillis 9y ago
  Radiative forcing from global warming will be somewhere between 2.6 and 6.0 Watts/m^2 by the end of the century[1]. Currently it is around 1.75 W/m^2[2], which translates to a total increase in absorption of 223 terawatts. That's about 3x the total energy produced by all photosynthesis[3][citation needed], and over 12x the energy in all forms consumed by humanity. So, to a first estimate, no. It's absolutely beyond what we're capable of. To a second estimate: these panels reject 70 W/m^2, so to counteract current warming we would need to cover .625% of the earth's surface in them, which is 3.2 million square kilometers, which is over 6x the area you'd need to replace all of humanity's energy use with solar power. All in all, it doesn't make much sense. [1]: https://en.wikipedia.org/wiki/Representative_Concentration_Pathways https://en.wikipedia.org/wiki/Representative_Concentration_P... [2]: https://en.wikipedia.org/wiki/Radiative_forcing#/media/File:Radiative-forcings.svg https://en.wikipedia.org/wiki/Radiative_forcing#/media/File:... [3]: https://en.wikipedia.org/wiki/Orders_of_magnitude_(power)#Terawatt_.281012_watts.29 https://en.wikipedia.org/wiki/Orders_of_magnitude_(power)#Te...
  - swsieber 9y ago
    Cool. I thought it wouldn't be feasible, but those numbers really help cement that idea. Thank you.
    - lucb1e 9y ago
      And thank you for asking :). I had the same question and the answer is fantastic. I really wish HN had some mechanism of extra upvotes, e.g. by being allowed to hand out one extra upvote per day or week, or by paying 5 cents (eur/usd) to buy an extra upvote (with a maximum of X per post or Y per day, or both, or whatever)... but alas.
biomcgary 9y ago
For a better scaling version of this technology (roll-to-roll manufacture), see: http://science.sciencemag.org/content/355/6329/1062 http://science.sciencemag.org/content/355/6329/1062
syntaxing 9y ago
Sky cooling is a super neat phenomena. It's one of the main reasons why sometimes at night, your car can frost even though the ambient temperature of the air is higher than freezing.
- gpvos 9y ago
  Sorry to be a pedant, but the singular form is phenomenon. Phenomena is the plural.
agumonkey 9y ago
Pretty neat idea. This reminds me of sun free photovoltaics. Somehow people managed to transform heat into coherent IR waves that could be converted by the usual PV cells.
- captainpete 9y ago
  Thermophotovoltaics :) https://en.wikipedia.org/wiki/Thermophotovoltaic https://en.wikipedia.org/wiki/Thermophotovoltaic
  - agumonkey 9y ago
    Yes this. For a reason I remember an article "sun free photovoltaics" hence my comment. But I can't find it again on this page.. odd. https://en.wikipedia.org/wiki/Sun-free_photovoltaics https://en.wikipedia.org/wiki/Sun-free_photovoltaics
SeriousM 9y ago
Meh. Get rid of the big cow farms and you have removed the biggest threat to the climate. This solution here is nice, but it's just a small amount compared to the big players.
- adrianN 9y ago
  Agriculture only contributes 10% or so in the US. Hardly the "biggest threat".
mizzao 9y ago
Couldn't beaming heat into space also buffer against global warming, as long as the amount of heat transmitted > the energy spent to beam it? Especially if we use renewable energy.
- kakarot 9y ago
  I think that's kind of just applying a bandaid to a wound that already has an infection. If you don't treat the underlying cause, (greenhouse gases) it's still going to get worse. Still, a massive planetary array of space radiators sounds badass.
  - beambot 9y ago
    At the risk over over-utilizing your metaphore... you still put on bandaids on infections -- even if you're taking antibiotics or applying antiseptic ointment.
frevd 9y ago
Does that mean we can cover the deserts with these plates that run purely on solar energy and release energy as infrared radiation to combat Global Heating?
- frevd 9y ago
  Ah, sorry, duplicate question (see below). Well, even if it does not do much, it's a start, and it shouldn't require putting in extra energy from power plants.
kardos 9y ago
Is there any material that readily absorbs heat at wavelengths between 8 and 13 micrometers? Instead of beaming the heat to space, could you instead put that special coating on a parabolic reflector and use it to heat up an absorbing material at the focal point? And then put a frying pan on top of that and cook an egg?
- analog31 9y ago
  There's a statement of the 2nd law of thermodynamics, that forbids you from passively transferring heat from a cold body to a hot body.
  - kardos 9y ago
    Ah of course. So best case it can accelerate warming cold things to ambient temperature
- mlonkibjuyhv 9y ago
  It's completely unnecessary. In a system capable of doing that, you might just as well boil your eggs at the source. Thermal equilibrium, and all.
dzonga 9y ago
I thought such a system already existed.
mrfusion 9y ago
I'd be curious if we could build a floating patch of these in the ocean and put them in front of hurricanes to rob them of the hot water they need to grow? Anyone able to do the math? Keep in mind all the billions we spend on hurricane damage.
- schiffern 9y ago
  It would be a lot cheaper to do some cloud seeding or SRM ahead of the storm to reflect away solar radiation into space. https://en.wikipedia.org/wiki/Solar_radiation_management https://en.wikipedia.org/wiki/Solar_radiation_management
aphextron 9y ago
Professor Fan has a few incredible, highly technical lectures about the subject on YouTube if anyone's interested.[0] His work centers on nanophotonics, which goes hand in hand with research surrounding photovoltaic cell efficiency as well. https://www.youtube.com/watch?v=Uazp_k_ckqc https://www.youtube.com/watch?v=Uazp_k_ckqc [0]
fulafel 9y ago
Howis this "20% energy savings" product different from their original "all passive" pitch[1] from 2014? https://spectrum.ieee.org/tech-talk/green-tech/solar/passive-radiators-cool-by-sending-heat-straight-to-outer-space https://spectrum.ieee.org/tech-talk/green-tech/solar/passive...

404 points by uoaei 9y ago

I think the biggest question here is what saves more dirty energy. Obviously, these units will compete with solar for roof space. The sun beats down in the summer, where these panels would be most useful, but also where solar would hit peak power generation. As long as solar can supply at least 20% of the power required to cool the building, it seems like it will be a better option, as solar is also useful for other things like charging electric cars during the winter, when A/C is not required.

jws 9y ago
Even on a flat roof, there is room to add radiator panels without compromising solar space. The solar panels will be tipped up to the south some amount based on their latitude, but you don't want to shade the low end of a panel with the high end of the next one, so there is a gap between rows. A shaded gap. Precisely the best spot to put radiator panels. You could even imagine a combined product which would be a corrugated panel alternating "uphill" solar and "downhill" radiator segments with the dimensions tailored to the latitude. This could be installed flat on the roof.
- dsr_ 9y ago
  180 degree flip panels. Solar cells during the day, IR radiators at night.
  - phinnaeus 9y ago
    Plus it would look super cool if you got them to flip in a wave pattern across your roof.
    - 0xfeba 9y ago
      I can see it now: malware communicating across air-gapped systems by way of flipping radiator panels on roofs.
      - Micoloth 9y ago
        Yes this has to be it
      - kerkeslager 9y ago
        After the CRISPR malware transmitted via actual genes, I'd barely be surprised.
        0xfeba 9y ago
        That was a lot of hype and not much else. They modified the machines that were reading the specially crafted DNA.
        nerpderp83 9y ago
        Life always finds a way.
- politician 9y ago
  Tesla's SolarCity product consists of rooftop tiles, some of which are not solar panels -- approx. 50%. Those non-collecting panels could be replaced with IR emitting panels without much change to their overall strategy.
DontGiveTwoFlux 9y ago
This assumes it is most efficient to build the solar locally. These radiative panels have to be installed locally. Solar can be transmitted over wires from large scale plants.

hourislate 9y ago

Simply putting your outside AC Condenser Unit on the shady side of a house or have a Tree or Bush shade it can significantly reduce your energy usage. They units themselves are at least 20 Degrees cooler than being in direct sunlight. There are also misting units that use approx 1-2 gallons of water a day (equivalent to a toilet flush) that can also reduce energy consumption by up to 30%. Simple solutions for big savings.

goda90 9y ago
Swamp coolers are useless in high humidity climates. And similarly, shade isn't as cool relative to direct sunlight in high humidity either.
- xenadu02 9y ago
  The water removes more heat from the coolant; the swamp cooler isn't for the inside of the house it's for the compressor itself.
bmcusick 9y ago
Your first claim was so interesting I had to Google it. But this article suggests it doesn't hold up. https://www.energyvanguard.com/blog/will-shading-your-air-conditioner-save-you-money https://www.energyvanguard.com/blog/will-shading-your-air-co... Moneyquote: "The temperature of the surrounding air has a much bigger effect on cooling efficiency than direct solar gain, and the volume of air pulled in by an air conditioner is huge."
- hourislate 9y ago
  This article you are referring to is for a heat pump and so are the % of savings. An AC Condenser sitting in the Sunlight will naturally be a lot hotter in temperature than one sitting in the shade. For example park your car in the sunlight and then park your car in the shade? Where will the surface of your vehicle be hotter/cooler? It has nothing to do with air temperature at this point. It is the heat of the sunlight that is raising the temp of the coils in the condenser just like it would raise the temp of the surface of a vehicle parked in the sun instead of the shade. I live in TX. I have some experience with this.

vtange 9y ago

If this system is scalable area-wise wouldn't it be a good idea to shield the ice caps with this? A 3C to 5C degree difference could mean quite a bit in preventing further ice melting, no?

kardos 9y ago
The Arctic and Antarctic are very big. If you could somehow build a structure that would withstand the harsh conditions, I imagine using a mirror or even aluminum foil would be an overwhelmingly cheaper way of reflecting energy back out.
goda90 9y ago
I believe I saw a test where they put a white sheet over some ice in Greenland, and came back a year later. The ice under the sheet was multiple inches higher than the surrounding ice.
jackhack 9y ago
But that's just it -- it is NOT scaleable to any measure that would make a difference. The manufacturing effort alone would require quantities of raw material that would dwarf all construction efforts ever undertaken combined. There is the issue of mining, refining, manufacturing, transporation... not to mention the installation and maintenance of a hundred thousand square miles of reflective shields in an incredibly hostile (to life) environment. Even if the whole of humanity could agree this is the most pressing issue of civilization, we would wreck the earth to save the ice. It would be easier to build a shopping mall at the bottom of the ocean. And the sun will just get warmer anyway. It is folly to think we can play God. Climate change is normal, and natural. It has been happening since the beginning of time, and will continue long after all traces of life on Earth are gone. Who are we to attempt to interfere?
- llukas 9y ago
  We already did play God by increasing CO2 in atmosphere. There is nothing wrong in efforts to mitigate its effect.

davidhyde 9y ago

A temperature drop of 3-5 degrees C is meaningless unless other variables are supplied. For example, how much water was cooled? They tell you how long (3 days) but they don't let you how many panels they used either. Too many 'science' articles these days don't add up.

philipkglass 9y ago
This is just a press release about the actual scientific publication. The abstract provides more information: https://www.nature.com/articles/nenergy2017143 https://www.nature.com/articles/nenergy2017143 Cooling systems consume 15% of electricity generated globally and account for 10% of global greenhouse gas emissions. With demand for cooling expected to grow tenfold by 2050, improving the efficiency of cooling systems is a critical part of the twenty-first-century energy challenge. Building upon recent demonstrations of daytime radiative sky cooling, here we demonstrate fluid cooling panels that harness radiative sky cooling to cool fluids below the air temperature with zero evaporative losses, and use almost no electricity. Over three days of testing, we show that the panels cool water up to 5 ∘C below the ambient air temperature at water flow rates of 0.2 l min−1 m−2, corresponding to an effective heat rejection flux of up to 70 W m−2. We further show through modelling that, when integrated on the condenser side of the cooling system of a two-storey office building in a hot dry climate (Las Vegas, USA), electricity consumption for cooling during the summer could be reduced by 21% (14.3 MWh). And you can read the full article via sci-hub to get all the experimental details.
- kbenson 9y ago
  > the panels cool water up to 5 ∘C below the ambient air temperature at water flow rates of 0.2 l min−1 m−2, corresponding to an effective heat rejection flux of up to 70 W m−2. Can someone translate that into layman terms? The chained negative exponents are somewhat confusing. I would think 70 W m^2 would me square meters, but what's 70 W m^-2? I assume it's not really mappable to dimensions at that point...
  - ar813 9y ago

deleted 9y ago

[deleted]

Cshelton 9y ago

Wouldn't it be more efficient to just use water run through a coil 6 ft underground? In most areas that have the intense heat that running water over the radiators actually would help, the ground 6 ft below is pretty easily cooler than 5-10 degrees C. The electricity to pump 6 ft down couldn't be that much more either... And when it isn't as hot out, you can actually use the ground temp to radiate heat out of the house by itself, no need for coils and a fan to run in ambient air temp, right?

fragsworth 9y ago
Maybe digging is impractical in a lot of situations?
renlo 9y ago
The problem is that with ACs/power plants, the net temperature will rise if you do this because it's a closed system. Power plants and ACs are not 100% efficient; the power plant converts chemical/nuclear/mechanical energy into electrical energy, releasing heat from work lost. Your AC will convert electrical energy to cool the air around you, but because it is not 100% efficient, the total temperature of the system will rise. There needs to be a way to get rid of that lost energy and remove it from the system. If you put that into the ground, it's still in the system. Ofc, even when they try to 'beam the heat to space', much of it will end up staying in the system (earth) as it reflects on clouds / water vapor, etc.
- Swizec 9y ago
  Isn’t this basically what happened with the London underground? It used to be cold down there now it’s super hot as the soil can’t absorb more heat. Source: https://www.forbes.com/forbes/welcome/?toURL=https://www.forbes.com/sites/lauriewinkless/2017/06/22/sweating-on-the-underground-why-are-tube-tunnels-so-hot/&refURL=https://www.google.com/&referrer=https://www.google.com/ https://www.forbes.com/forbes/welcome/?toURL=https://www.for... > According to this article in Rail Magazine, the average temperature inside the tunnels was around 14° in 1900. > increased the temperature of the surrounding clay so much that, today, average tunnel temperatures are between 20-25°C.

pavement 9y ago

into space Hmmm, that seems like a click-bait statement. Between the air conditioner and even low earth orbit, there's plenty of atmosphere that will soak up some of the beam's heat, no?

mikeyouse 9y ago
No offense, but did you read the article? It's directly addressed: > So Raman and electrical engineering professor Shanhui Fan made panels containing layers of silicon dioxide and hafnium oxide on top of a thin layer of silver. These radiate in a unique way: They send heat directly into space, bypassing the Earth’s atmosphere. The panels do this by emitting heat at infrared wavelengths between 8 and 13 micrometers. To these waves, the Earth’s atmosphere is transparent. What’s more, the panels reflect nearly all the sunlight falling on them. A little further research shows that the atmosphere is opaque at numerous wavelengths and it's probably safe to assume that they intentionally targeted the opaque ones: https://i.imgur.com/eUmTltm.png https://i.imgur.com/eUmTltm.png
- iRobbery 9y ago
  While i understand you both. A title is a title. And the title claims 'heat' not reflecting infrared wavelengths between 8 and 13 micrometers. And imho 'heat' is more then certain ranges of infrared wavelengths. So in that sense i can see why somebody uses the word clickbait in regards to this title. edit joke While i'm just afraid the moon will start to condensate /edit
  - kbenson 9y ago
    It's removing heat from a system by radiating it into space. That it's radiated using infrared is irrelevant, since it does cool the system it is attached to. Even "beam" is appropriate in this instance. There's no "bait" in the "click-bait", it's exactly as advertised.
    - pavement 9y ago
      Listen, a little tl;dr is not too much to ask for around here, especially when the salient point is buried 7 paragraphs in, when it should be present in the leading sentence. Forgive me for not locating the relevant passage, while quickly skimming this and 100 other articles, while at work. Furthermore, regarding cloud cover, I am dubious of the premise that even the specified wavelengths penetrate otherwise opaque cloud cover. Sure, maybe that portion of the spectrum penetrates the typical atmospheric mix, including light water vapor, on an otherwise clear day, but, color me unsurprised if it fails to penetrate smog, diesel and particulate pollution, and other common dust constituents in cloud nuclei. I mean, even radar can be blinded by dense storm clouds. But hey, maybe I'm wrong, maybe it's a 100% miracle cure. Maybe it's that awesome. I hope I really am just a big dummy, too lazy to read a blurb more than three sentences long.

leggomylibro 9y ago

Huh - I'm always interested in ways to make A/C more energy efficient. Squeezing and un-squeezing gas seems so COMPLICATED compared to how easy it is to heat things up. Entropy is a cruel mistress. Anyways, it sounds like this is the important bit: - So Raman and electrical engineering professor Shanhui Fan made panels containing layers of silicon dioxide and hafnium oxide on top of a thin layer of silver. These radiate in a unique way: They send heat directly into space, bypassing the Earth’s atmosphere. The panels do this by emitting heat at infrared wavelengths between 8 and 13 micrometers. To these waves, the Earth’s atmosphere is transparent. What’s more, the panels reflect nearly all the sunlight falling on them. For the new fluid-cooling system, the researchers made radiative panels that were each one-third of a square meter in area; they attached the panels to an aluminum heat exchanger plate with copper pipes embedded in it. The setup was enclosed in an acrylic box covered with a plastic sheet. The team tested it on a rootop on the Stanford campus. Over three days of testing, they found that water temperatures went down by between 3- and 5 °C. The only electricity it requires is what’s needed to pump water through the copper pipes. Water that flowed more slowly was cooled more. - So it sounds like how space stations kick out heat; The ISS uses that sort of thing[1]. You flow coolant through things that heat up, like solar panels or a warm environment, and then you pump it into these bricks that don't absorb heat from light. The coolant warms up the bricks, which emit that heat as infrared radiation. Planetside, I guess that you can't let the infrared radiation be absorbed by the atmosphere, or it won't cool anything. So, maybe this could take the compression out of our current cooling systems - compress/heat up, expose to outside temp, let cool, decompress/cool, expose to inside temp, repeat. My main question would be, is it capable of cooling beyond the ambient outside temperature? If so, how? I might be misunderstanding or missing something about how the 'blasting energy away as IR radiation' thing works. [1]: http://www.lockheedmartin.com/us/products/HeatRejectionRadiators.html http://www.lockheedmartin.com/us/products/HeatRejectionRadia...

ar813 9y ago
I'm one of the authors / people working on this. Yep, radiators like the ones on the ISS are pretty much the dominant/only ways to get heat out in space. In response to your questions: yes, it can in fact cool below the ambient air temperature entirely passively (even during the day! -- which adds real value for cooling applications). We've shown in other recent work that you can use this effect to cool as much as 45-50°C below the ambient air temperature, if you insulate the radiator perfectly. The reason this works here on Earth is that some upward thermal radiation isn't absorbed and re-emitted back to you. So if you start at the air temperature, looking upwards, you will be sending more heat out than the sky sends back to you. This allows an upward-looking surface to cool itself down until the heat going out and coming back to it balance out.

ChuckMcM 9y ago

I am super excited they built a practical demonstration system out of this technology. I would love it if more 'breakthrough' research took it to this sort of proof of concept (I know it is hard to get funding for that sort of project but it is so useful). I would love to see self contained shade structures that would both shade and lightly cool the air underneath them.

jmh530 9y ago

How much does this save vs. replacing these panels with solar panels?

fpoling 9y ago

Atmosphere is only transparent for thermal infrared without clouds. Clouds emits and reflects ambient heat back to these panels heating them. But then one does not need typically air-conditioning on a cloudy day :)

firebird84 9y ago
Depends on where you live. :) Where I am, clouds do nothing.
- lucb1e 9y ago
  Interesting! Do you know some examples of places where clouds influence temperature a lot and where it doesn't? And what causes this?
  - Roverlord 9y ago
    Maybe it's typical cloud base height?

seanalltogether 9y ago

If these become popular, maybe you could create a new solar panel that absorbs the wavelengths emitted by these air conditioners in order to create electricity ...or better yet...

hwillis 9y ago
These panels reject heat at a rate of up to 70 W/m^2. A good solar panel absorbs 20% of incoming light, which typically peaks at about 1000 W, so a solar panel reduces temperature by 3x as much. So... you could just do that.
- irrelative 9y ago
  Furthermore, air conditioning isn't lowering the temperature of a system by the energy consumed. Rather, it acts like a heat pump which usually pumps more energy that is used. So 200 J/s of electric power running a typical AC unit would likely reject more than 200 J/s from a building.
paddy_m 9y ago
Could you create a solar panel that generates energy during the day and rejects heat during the night? Would it be efficient at either task?
the8472 9y ago
Solar panel efficiency decreases with rising temperatures, so maybe increasing its emissivity in the infrared window could improve efficiency.

swsieber 9y ago

Question - could one theoretically build a big enough array of this to counter-act globally warming? Any back of the envelope math for what it would take would be very interesting.

hwillis 9y ago
Radiative forcing from global warming will be somewhere between 2.6 and 6.0 Watts/m^2 by the end of the century[1]. Currently it is around 1.75 W/m^2[2], which translates to a total increase in absorption of 223 terawatts. That's about 3x the total energy produced by all photosynthesis[3][citation needed], and over 12x the energy in all forms consumed by humanity. So, to a first estimate, no. It's absolutely beyond what we're capable of. To a second estimate: these panels reject 70 W/m^2, so to counteract current warming we would need to cover .625% of the earth's surface in them, which is 3.2 million square kilometers, which is over 6x the area you'd need to replace all of humanity's energy use with solar power. All in all, it doesn't make much sense. [1]: https://en.wikipedia.org/wiki/Representative_Concentration_Pathways https://en.wikipedia.org/wiki/Representative_Concentration_P... [2]: https://en.wikipedia.org/wiki/Radiative_forcing#/media/File:Radiative-forcings.svg https://en.wikipedia.org/wiki/Radiative_forcing#/media/File:... [3]: https://en.wikipedia.org/wiki/Orders_of_magnitude_(power)#Terawatt_.281012_watts.29 https://en.wikipedia.org/wiki/Orders_of_magnitude_(power)#Te...
- swsieber 9y ago
  Cool. I thought it wouldn't be feasible, but those numbers really help cement that idea. Thank you.
  - lucb1e 9y ago
    And thank you for asking :). I had the same question and the answer is fantastic. I really wish HN had some mechanism of extra upvotes, e.g. by being allowed to hand out one extra upvote per day or week, or by paying 5 cents (eur/usd) to buy an extra upvote (with a maximum of X per post or Y per day, or both, or whatever)... but alas.

biomcgary 9y ago

For a better scaling version of this technology (roll-to-roll manufacture), see: http://science.sciencemag.org/content/355/6329/1062 http://science.sciencemag.org/content/355/6329/1062

syntaxing 9y ago

Sky cooling is a super neat phenomena. It's one of the main reasons why sometimes at night, your car can frost even though the ambient temperature of the air is higher than freezing.

gpvos 9y ago
Sorry to be a pedant, but the singular form is phenomenon. Phenomena is the plural.

agumonkey 9y ago

Pretty neat idea. This reminds me of sun free photovoltaics. Somehow people managed to transform heat into coherent IR waves that could be converted by the usual PV cells.

captainpete 9y ago
Thermophotovoltaics :) https://en.wikipedia.org/wiki/Thermophotovoltaic https://en.wikipedia.org/wiki/Thermophotovoltaic
- agumonkey 9y ago
  Yes this. For a reason I remember an article "sun free photovoltaics" hence my comment. But I can't find it again on this page.. odd. https://en.wikipedia.org/wiki/Sun-free_photovoltaics https://en.wikipedia.org/wiki/Sun-free_photovoltaics

SeriousM 9y ago

Meh. Get rid of the big cow farms and you have removed the biggest threat to the climate. This solution here is nice, but it's just a small amount compared to the big players.

adrianN 9y ago
Agriculture only contributes 10% or so in the US. Hardly the "biggest threat".

mizzao 9y ago

Couldn't beaming heat into space also buffer against global warming, as long as the amount of heat transmitted > the energy spent to beam it? Especially if we use renewable energy.

kakarot 9y ago
I think that's kind of just applying a bandaid to a wound that already has an infection. If you don't treat the underlying cause, (greenhouse gases) it's still going to get worse. Still, a massive planetary array of space radiators sounds badass.
- beambot 9y ago
  At the risk over over-utilizing your metaphore... you still put on bandaids on infections -- even if you're taking antibiotics or applying antiseptic ointment.

frevd 9y ago

Does that mean we can cover the deserts with these plates that run purely on solar energy and release energy as infrared radiation to combat Global Heating?

frevd 9y ago
Ah, sorry, duplicate question (see below). Well, even if it does not do much, it's a start, and it shouldn't require putting in extra energy from power plants.

kardos 9y ago

Is there any material that readily absorbs heat at wavelengths between 8 and 13 micrometers? Instead of beaming the heat to space, could you instead put that special coating on a parabolic reflector and use it to heat up an absorbing material at the focal point? And then put a frying pan on top of that and cook an egg?

analog31 9y ago
There's a statement of the 2nd law of thermodynamics, that forbids you from passively transferring heat from a cold body to a hot body.
- kardos 9y ago
  Ah of course. So best case it can accelerate warming cold things to ambient temperature
mlonkibjuyhv 9y ago
It's completely unnecessary. In a system capable of doing that, you might just as well boil your eggs at the source. Thermal equilibrium, and all.

dzonga 9y ago

I thought such a system already existed.

mrfusion 9y ago

I'd be curious if we could build a floating patch of these in the ocean and put them in front of hurricanes to rob them of the hot water they need to grow? Anyone able to do the math? Keep in mind all the billions we spend on hurricane damage.

schiffern 9y ago
It would be a lot cheaper to do some cloud seeding or SRM ahead of the storm to reflect away solar radiation into space. https://en.wikipedia.org/wiki/Solar_radiation_management https://en.wikipedia.org/wiki/Solar_radiation_management

aphextron 9y ago

Professor Fan has a few incredible, highly technical lectures about the subject on YouTube if anyone's interested.[0] His work centers on nanophotonics, which goes hand in hand with research surrounding photovoltaic cell efficiency as well. https://www.youtube.com/watch?v=Uazp_k_ckqc https://www.youtube.com/watch?v=Uazp_k_ckqc [0]

fulafel 9y ago

Howis this "20% energy savings" product different from their original "all passive" pitch[1] from 2014? https://spectrum.ieee.org/tech-talk/green-tech/solar/passive-radiators-cool-by-sending-heat-straight-to-outer-space https://spectrum.ieee.org/tech-talk/green-tech/solar/passive...