13 ms·

“Cold Tube” cooling system uses half the energy of an air conditioner

124 points by bornelsewhere 6y ago

klyrs 6y ago
This sounds pretty neat, but their description of cold things sucking thermal radiation doesn't jive with my freshman-physics understanding of thermodynamics. AFAICT they've got cold water circulating in a moisture-repellent membrane, so they're able to absorb heat by chilling the water in the pipes instead of fussing with the humidity in the air like most AC does. So it sounds like trading inefficiency of standard AC units for an inefficient thermal interface -- you need to stand next to it to feel cooled?
- upofadown 6y ago
  It might be better to think of it as creating an environment where you are not surrounded by warm objects radiating at you. So it should not matter where you are in the space or how large it is. The effect should be the same.
- foxyv 6y ago
  About 60% of human body heat is lost through radiation. The cooling you would feel would be proportional to the percentage of the area around you that is covered by these cooling walls. Distance wouldn't cause that much loss because the air doesn't absorb much radiation in blackbody range of humans over distances less than 50 meters.(Infrared range with intensity peaking at 93 thousand angstroms)
  - mrfusion 6y ago
    But when I lose that heat through radiation it would presumably bounce around the room and not much reflects back onto my body. So I’m not seeing how much this really helps. My radiated heat shouldn’t be returning to me anyway.
    - cjhveal 6y ago
      Also not sure how effective this system really is, but it helped me to imagine my walls reflecting visible light as if I were in a room of mirrors and thinking about how many higher order reflections of myself would be able to reach just my pupil, multiplied by the surface area of my body.
    - Majromax 6y ago
      You lose heat through radiation, but the materials surrounding you are also radiating heat. You emit thermal radiation at a black-body temperature of 37C or so to the environment, but the average surface nearby (in a non-air-conditioned environment) will be radiating back at 30C or so, for very little net heat loss. The innovation described here is to replace the local environment with a chilled one that interacts only by radiation. The air with very little mass contributes negligible radiation to the system, so you radiate heat outwards but receive little in return.
- tripletao 6y ago
  It's the cooling equivalent of a radiant heater, and you need line-of-sight to the walls to feel cooled. The thermal interface is deliberately inefficient for convection (to avoid wasting power chilling the air), but efficient for radiation. Radiation is proportional to absolute temperature T^4. So compared to a glowing radiant patio heater, I'd expect to need maybe (1000^4 - 300^4)/(300^4 - 270^4) ~ 350x the area for the same heat transfer in the opposite direction, thus their big tunnel instead of a little filament. Even with their cold source at absolute zero, they'd still need >100x.
  - sparker72678 6y ago
    And you still have to pump the heat out to somewhere else. The whole premise with this system is that you can keep the temperature higher so you have to pump less heat, which I'm extremely skeptical of, at least for indoor environments.
    - URSpider94 6y ago
      The biggest gain is that you don’t have to pump out all of the heat of condensation of all of the moisture in the air. Condensing out a pound of water is 200x more energy-consuming than lowering the temperature of a kg of air by 10 degrees C.
  - kuzee 6y ago
    Thanks for explaining. I am also surprised by this possibility given my limited physics knowledge. Do clothes substantially reduce the effectiveness? Is true line of sight required - visible or near visible spectrum? Secondly, can you expand a bit about the humidity/condensation aspect? I get the impression that condensation represents inefficiency, and that this somehow avoids having to cool air as a middle layer to cooling a person.
    - tripletao 6y ago
      A cubic meter of air around room temperature and pressure has mass around 1000 g, and isobaric specific heat capacity around 1 J/(g*K). So cooling that air from 30 C to 25 C requires us to suck out 5 kJ. But at 30 C and 100% RH, air holds roughly 30 g/kg of water, while at 25 C it can hold only 20 g/kg. So as we cool the air, 10 g of water will condense, releasing about 20 kJ that we also have to suck out. There's no way to cool the air without condensing the water. In my example, the "latent" heat from the water condensing was much bigger than the "sensible" heat from air cooling. In practice it seems the latent heat is typically around 25% of the total[1], since we're probably at <100% RH, and since heat probably leaks in faster than moisture does (since air leaks let in both heat and moisture, but conduction through the walls/windows lets in only heat). The latent heat would be a bigger contributor in the poorly-sealed or outdoor cooling applications that these researchers seem to be targeting. The idea of a radiant cooling tunnel appears to be old, but not very popular because it's not very effective. The cold plates leak cold into the air, just becoming a more cumbersome version of conventional air conditioning. The cold plate also can't run colder than the dew point, since the condensed water would drip and make a mess. The innovation here seems to be that they've placed a thermally non-conductive but transparent (to the thermal radiation) membrane between the cold plate and the user. There's a thin layer of cold, dry air between the cold plates and the membrane, but the membrane stops the cold from leaking out into the room air. It's analogous to the sun shining through a well-insulated window on a winter day--you still feel the radiative heating from the sun, even as the window keeps the warm and cool air separated. Normal window glass wouldn't work for the cooling case, since the heat source isn't the sun (~6000 K) but the human (~300 K), so the wavelengths are much longer, around 10 um, and window glass is opaque there. Plastics with transmission around there are known, though, like the ones used to make the Fresnel lenses for PIR motion detectors. In any case, that membrane lets them keep the cold plate colder than the dew point without condensing water onto it, and also decreases loss of cooling by convection into the air. It would work best on exposed skin. It should still work with clothes, as long as the clothes aren't too thermally insulating. 1. https://www.energy.gov/sites/prod/files/2013/12/f5/issue7_sensible_loadcontrol.pdf https://www.energy.gov/sites/prod/files/2013/12/f5/issue7_se...
- m463 6y ago
  Gaining or losing heat via radiation isn't as easy as conduction, but it does work. It's possible to make ice at night in temperate climates by taking the equivalent of a solar concentrator, putting water at the focus and pointing it at a dark patch of clear sky. You know, probably standing in the sun vs shade is probably the opposite analogy. In the sun you get radiative heating from the sun, in the shade you just get heating from the nearby air.
- outworlder 6y ago
  > but their description of cold things sucking thermal radiation doesn't jive with my freshman-physics understanding of thermodynamics. Pseudoscience alarms started to sound in my head, until I read the comments. If I understood this correctly - you will still radiate heat as normal. But, since the thermal radiation you emit will reach these things (assuming line of sight), you won't have much reflected back at you (or at nearby objects, which would heat them up). And so, you feel colder, even though the air is not being chilled. That would make sense, similar to how we can make ice during the night even in a desert. You can radiate heat into space(as not all thermal radiation will be absorbed by the air) https://tecped.com/process-of-freezing-ice-in-the-desert-according-to-physicists/ https://tecped.com/process-of-freezing-ice-in-the-desert-acc...
- colechristensen 6y ago
  From a freshman physics point of view, “sucking” is also not a pull-from-low process but a push-from-high process. There is some nuance there but simply, a straw doesn’t work right in a vacuum.
- alacombe 6y ago
  > fussing with the humidity in the air like most AC does Humidity will have to be dealt with no matter what, either by the AC system, or though condensation, as cold air holds less water vapour as warm air.
growlist 6y ago
Pretty cool (sorry)
sparker72678 6y ago
> The notoriously bad energy efficiency of air conditioners Air conditioners are actually pretty fantastically efficient for what they do. The problem with air conditioners is that there's no way to move a ton of heat without using a lot of energy. So, they do use a lot, but they make the most of it. What's truly bad are our buildings that have the minimal insulation and sealing possible, leaking all that cold air right back out into the environment.
- ianai 6y ago
  There’s also no obvious market factor incentivizing modernization of old RE let alone efficiency.
- eggsnbacon1 6y ago
  New buildings are rather efficient in US. The problem is old buildings that use 5X the energy for HVAC. I echo that AC is quite efficient. Far more efficient than traditional heating. There's a misconception that hot areas are less environmentally friendly due to AC. The opposite is true. Hot areas are only 25 freedom units hotter than humans prefer. Cold areas have months of 50+ temperature difference. The misconception persists because heat uses gas, which is 5-10X less expensive per BTU of energy than electricity. So it might be cheaper to heat cold areas than run AC in hot ones, but its much more damaging to the environment. Plus, hot climates are using a lot of renewables these days which impacts the environmental friendliness of electric but not gas. I expect migration to the sun belt to accelerate, at least in the US. It makes a lot of sense from environmental perspectives. In some southern cities there's already long stretches every summer where daytime AC use runs on 70%+ renewable energy.
  - marcinzm 6y ago
    [I was wrong]
    - roywiggins 6y ago
      Air conditioners are often more than 100% efficient- they move more heat energy than they consume. (Of course if you start with a fossil fuel, turn it into electricity, and then pipe that into an AC unit, the overall efficiency will be dropped by the efficiency of the power plant, but it's still somewhat made up for by the advantages of heat pumps)
zbyte64 6y ago
I wonder how costly it is to fill your walls entirely with water pipes. Also, one currently ensures there is a stud or lack of electrical when putting nails in a wall. I guess you gotta hang things up differently.
- sparker72678 6y ago
  There are some "radiant cooling" installations out there. Most use either the ceiling or the floor, for the reasons you point out.
  - stephen_g 6y ago
    Yeah, my brother used to work in a building that was cooled like this with a 'chilled beam' system - https://en.wikipedia.org/wiki/Chilled_beam https://en.wikipedia.org/wiki/Chilled_beam Apparently it works pretty well.
    - istjohn 6y ago
      That uses a different mechanism. It cools the air and relies on convection. TFA specifically avoids cooling the air.
- alacombe 6y ago
  > I wonder how costly it is to fill your walls entirely with water pipes. Pretty costly in water damages for sure, people tends to drive nails in pipes all the time already, just imagine this * 100x.
Stierlitz 6y ago
> .. as a person stands next to or beneath the panel, the body heat radiates towards the chilled panels to create a cooling sensation .. I'm not sure that is an accurate description of the physics. Maybe the air next to the panel is cooler, accounting for the cooling sensation.
- yummypaint 6y ago
  The cold air will contribute, but this is an accurate description. A person constantly radiates a blackbody spectrum determined by temperature, as does the surrounding room. We perceive ourselves as in equilibrium when we radiate as much as we receive. If a wall is cooler than the rest of the room, the person receives less infrared from that direction and perceives cold, even in the absence of convection.
- thefiregecko 6y ago
  This confused me for a bit. The point of the system is to prevent energy from being reflected or radiated from a surface. Systems like this have been around for a while (https://www.energy.gov/energysaver/home-cooling-systems/radiant-cooling https://www.energy.gov/energysaver/home-cooling-systems/radi...), the news here is that this works with temperatures below the dew point because they have solved the condensation issues.
andor 6y ago
Not sure why they are researching the mechanism, these systems are commonly installed in Germany and known as "Kühldecke" (cooling ceiling). https://de.wikipedia.org/wiki/K%C3%BChldecke https://de.wikipedia.org/wiki/K%C3%BChldecke
- justinclift 6y ago
  Is this the same kind of thing? (english wikipedia) https://en.wikipedia.org/wiki/Chilled_beam https://en.wikipedia.org/wiki/Chilled_beam
- ladberg 6y ago
  This is a bit different. A cooled ceiling cools the air through convection, but this isn't supposed to. Instead, it basically just "removes" the warm walls you'd experience in any other setting. A cooled ceiling would cool more effectively but possibly not as efficiently.
- ac42 6y ago
  The WP article points out the issue of condensation, which the OP claims as being addressed in a novel way.
LifeIsThermal 6y ago
Notice how the system cools by absorbing heat from a body, but the greenhouse theory says that the earth surface warms from air absorbing heat from it. The GHE is pseudo-science.
- aaron695 6y ago
  My new rule is upvote anyone who segues into anti-global warming statements on articles that don't mention Global Warming. Because I'm sick to death of every time an efficiency is mentioned people have to bring out their favourite religion because we all forgot about Global Warming since a hour ago. I'm also impressed you waited 3 years to comment.
- ladberg 6y ago
  The cooling system doesn't magically cool itself, it uses cold water to remove the heat that's added by radiation from people near it. This has nothing to do with the greenhouse effect (which occurs when you have two bodies of drastically different temperatures with an air barrier).
finphil 6y ago
This sounds promising. I wonder if such can be implemented in small dwellings.
csours 6y ago
I'm not an expert, if one is available please comment. Human perception of temperature is mostly based on 5 things: Ambient air temperature, Radiant Heat (infrared radiation), humidity, direct conduction of heat, and air movement. It seems like this addresses Radiant Heat. Another way to address this is to add more insulation, install low-emissivity windows, plant shade trees in your yard. Half of my house feels much warmer in the afternoon because it lacks shade. I used a thermometer to see the difference between the ambient air temperature in the two halves; the hot side was only 2 degrees F hotter. I don't have an IR thermometer, but I imagine that the walls in the hot side are at least 10 degrees F hotter.
username505 6y ago
This is just a geothermal unit with the evaporator built around the load and instead of air to air transfer through convection it is air to air transfer through radiation... nothing but smoke and mirrors. The problem with efficiency and A/C is the excess heat generated by the compression element of the Refrigeration Cycle. The closest thing to 100% efficiency is achieved through absorption chillers that utilize an internal chemical reaction based off of external heat to produce compression through a metered system... neat idea though. Heating systems that utilize the same process are different though - you can achieve greater than 100% efficiency with the use of flash gas bypass designs that will say for example produce 1.5 tons of heat in a 1 ton system.
ladberg 6y ago
The author doesn't really explain it well because his explanation breaks some physics laws, so it doesn't "suck" your body heat away. Instead, it lowers the amount of heat radiating onto you from your environment by replacing hot walls with cold walls, which will lower the temperature of your skin. It's efficient specifically because it doesn't cool by convection (like every other cooler). This allows the designers to insulate it so they only have to offset temperature gained by incoming heat radiation when keeping it cool. That also means it won't cool the air, just the objects near it.
- labawi 6y ago
  Thermal radiative coupling is bidirectional. Sucking away is appropriate and important as you do actually have to displace the energy somewhere. It works the same way when sucking air. A simpler non-radiating equivalent would be a reflective foil, or a polished metal - you could enclose yourself within it, get no radiating heat from environment, yet it wouldn't help cool you, because your radiation has no place to go.
  - ladberg 6y ago
    I still feel like "sucking" is misleading because it doesn't change how much heat you radiate, only how much heat is radiated on to you. A better analogy would be like a curtains for heat.
    - ants_a 6y ago
      I think that the analogy is used because people underestimate how much heat is lost to radiation. Human body radiates energy away at about 800W. It's not noticeable, because normally it is balanced by a similar flux of thermal radiation coming in from the environment. If the apparent radiative temperature of the environment is reduced it can indeed feel like it is sucking heat out.
      - CorrectHorseBat 6y ago
        You're off by about an order of magnitude there. The human body uses ~10MJ per day which is ~100W. This not only includes radiation losses but also convection and evaporation.
OminousWeapons 6y ago
This sounds like they reinvented a swamp cooler. Am I missing something?
- pengaru 6y ago
  There is absolutely nothing resembling a swamp cooler going on here.
heisenzombie 6y ago
An idea I was told about relatively recently that kind of blew my mind: - Space is cold (~3K) - The atmosphere is really quite transparent in the wavelegth 8-13 μm - If one can construct an optical filter (e.g. grating) which is highly reflective except for a bandpass at 8-13μm, it is possible to reflect most solar energy but still "see" the cold of deep space - It's possible to build a box with sufficiently low thermal conduction, and this 'magic mirror' on top, to effectively refrigerate its contents by radiation to space. This uses no power, and works in direct sunlight [^1]. So weird, probably not very practical (what about cloudy days?), but very cool! [^1] in fact, if you put it in the shade then it would warm up because it could no longer radiate to space.
- MengerSponge 6y ago
  https://www.nature.com/articles/ncomms13729 https://www.nature.com/articles/ncomms13729
- Aperocky 6y ago
  Space is without temperature. Temperature is an attribute of things, space is a lack of things. What you're referring to is the temperature of cosmic background radiation, which is akin to how you emit infrared radiation at your body temperature. But you certainly don't classify the space where this radiation move through as having your body temperature. The two things are not the same imo.
  - heisenzombie 6y ago
    "Temperature" is a slippery word that has many different definitions depending on what area of physics you're working in. In this case it is perfectly fine to refer to "the temperature of space" since you're explicitly using it as a cold sink. As evidence, see the paper (published in Nature no less!) that MengerSponge posted. The authors say "On the other hand, outer space, at a temperature of 3 K, provides a much colder heat sink."
    - Aperocky 6y ago
      Here's something I don't understand though, if we put a blackbody in deep space, would it eventually be cooled/heated to the temperature of the cosmic background radiation? The space around us is filled with photon coming from Sun at ~5500K, but it doesn't heat anything to anywhere near that. So given the current density of cosmic background radiation at 411 photon cm -3, would it be sufficient to place a blackbody to the equilibrium temperature? I am not a physicist by training, and this is a genuine question.
abrowne0 6y ago
This is just a regular hydronic radiant system which is very efficient because it doesn’t need to heat the air. The thing is, hydronic systems have been around for 70 years or more but they typically are not used for cooling because of the humidity issues that arise which are damaging to the building. So this can only be implemented in buildings with materials resistant to water damage. Hydronic radiant systems are the best around it terms of heating efficiency but very expensive to install. This article seems like hype and bs.
- abrowne0 6y ago
  It does say that there is a Novel membrane to prevent humidity build up, but there isn’t a lot of information about the membrane and what conditions it will work in. For instance, Will it work in a wooden structure with drywall?
adrianmonk 6y ago
This sounds expensive to install. For it to work as well as regular AC, wouldn't this have to be built into basically all the walls in your home?
infogulch 6y ago
This is pretty neat. It lets you (somewhat) decouple the temperature and humidity of the air from how cool it feels to be in the room, by only removing radiative heat coming from inside the room. You could choose to exchange air with the outside more rapidly without losing efficiency because you aren't putting as much energy into conditioning the air itself. I wonder if there are any infrared-transparent wall paints.
kristopolous 6y ago
I saw a very promising AC technology at CES in january that people may find interesting: https://www.oxicool.com/ https://www.oxicool.com/ I don't have the material science or chemistry background to know how effective it is, but I hope everything they claim holds water, it sounds pretty good. There's also a DIY water based AC with pipes and a cheap pump you can find widely on the internet, but I haven't done it yet. Here's an example https://www.instructables.com/id/Hollis-homemade-AC/ https://www.instructables.com/id/Hollis-homemade-AC/ ... In the comments one poster suggested a toilet tank as a reservoir, that sounds promising.
- yourapostasy 6y ago
  That's neat and I'm going to keep an eye on it. The -15° F ambient differential somewhat limits its usefulness, and I'd like to see an induction-powered heater as an option instead of conduction-based heating. I'm guessing the 10-year lifespan is due to the fan bearings and the molecular sieve lifetime, and I'd like to see the overall system lifespan increased by 10X. Would be interested in the papers behind this tech, as I think there are a lot of caveats they're glossing over. [1] seems to be a paper on adjacent technology. [2] seems to indicate the service lifetime of the molecular sieve is the controlling factor in the estimated lifecycle. 10 years sounds like the upper range. [1] https://aip.scitation.org/doi/abs/10.1063/1.4822041?journalCode=rse https://aip.scitation.org/doi/abs/10.1063/1.4822041?journalC... [2] http://www.yyindustry.com/news_show.asp?id=28 http://www.yyindustry.com/news_show.asp?id=28
  - kristopolous 6y ago
    They're trying to get version 1 out the door. Hopefully there's a dramatic improvement and optimization curve still available given it's such early days still
- leoedin 6y ago
  They bury it slightly, but in the FAQ: "The primary energy for HomeCool™ is derived from clean open flame burn of natural gas. This can be converted with an optional kit to propane and also hydrogen* (*once commercially available)." It burns gas. It may work in a similar manner to absorption refrigerators often found in RVs. https://en.wikipedia.org/wiki/Absorption_refrigerator https://en.wikipedia.org/wiki/Absorption_refrigerator Burning gas isn't exactly a clean energy source. In fact, we need to be aggressively exploring ways to stop burning gas for heating - not starting to burn more for cooling!
tobyhinloopen 6y ago
Description seems like a thing from a science fiction.
b0rsuk 6y ago
Circulating fan uses tenth the energy of an air conditioner. The Revenge of the Circulating Fan https://www.lowtechmagazine.com/2014/09/circulating-fans-air-conditioning.html https://www.lowtechmagazine.com/2014/09/circulating-fans-air...

124 points by bornelsewhere 6y ago

This sounds pretty neat, but their description of cold things sucking thermal radiation doesn't jive with my freshman-physics understanding of thermodynamics. AFAICT they've got cold water circulating in a moisture-repellent membrane, so they're able to absorb heat by chilling the water in the pipes instead of fussing with the humidity in the air like most AC does. So it sounds like trading inefficiency of standard AC units for an inefficient thermal interface -- you need to stand next to it to feel cooled?

upofadown 6y ago
It might be better to think of it as creating an environment where you are not surrounded by warm objects radiating at you. So it should not matter where you are in the space or how large it is. The effect should be the same.
foxyv 6y ago
About 60% of human body heat is lost through radiation. The cooling you would feel would be proportional to the percentage of the area around you that is covered by these cooling walls. Distance wouldn't cause that much loss because the air doesn't absorb much radiation in blackbody range of humans over distances less than 50 meters.(Infrared range with intensity peaking at 93 thousand angstroms)
- mrfusion 6y ago
  But when I lose that heat through radiation it would presumably bounce around the room and not much reflects back onto my body. So I’m not seeing how much this really helps. My radiated heat shouldn’t be returning to me anyway.
  - cjhveal 6y ago
    Also not sure how effective this system really is, but it helped me to imagine my walls reflecting visible light as if I were in a room of mirrors and thinking about how many higher order reflections of myself would be able to reach just my pupil, multiplied by the surface area of my body.
  - Majromax 6y ago
    You lose heat through radiation, but the materials surrounding you are also radiating heat. You emit thermal radiation at a black-body temperature of 37C or so to the environment, but the average surface nearby (in a non-air-conditioned environment) will be radiating back at 30C or so, for very little net heat loss. The innovation described here is to replace the local environment with a chilled one that interacts only by radiation. The air with very little mass contributes negligible radiation to the system, so you radiate heat outwards but receive little in return.
tripletao 6y ago
It's the cooling equivalent of a radiant heater, and you need line-of-sight to the walls to feel cooled. The thermal interface is deliberately inefficient for convection (to avoid wasting power chilling the air), but efficient for radiation. Radiation is proportional to absolute temperature T^4. So compared to a glowing radiant patio heater, I'd expect to need maybe (1000^4 - 300^4)/(300^4 - 270^4) ~ 350x the area for the same heat transfer in the opposite direction, thus their big tunnel instead of a little filament. Even with their cold source at absolute zero, they'd still need >100x.
- sparker72678 6y ago
  And you still have to pump the heat out to somewhere else. The whole premise with this system is that you can keep the temperature higher so you have to pump less heat, which I'm extremely skeptical of, at least for indoor environments.
  - URSpider94 6y ago
    The biggest gain is that you don’t have to pump out all of the heat of condensation of all of the moisture in the air. Condensing out a pound of water is 200x more energy-consuming than lowering the temperature of a kg of air by 10 degrees C.
- kuzee 6y ago
  Thanks for explaining. I am also surprised by this possibility given my limited physics knowledge. Do clothes substantially reduce the effectiveness? Is true line of sight required - visible or near visible spectrum? Secondly, can you expand a bit about the humidity/condensation aspect? I get the impression that condensation represents inefficiency, and that this somehow avoids having to cool air as a middle layer to cooling a person.
  - tripletao 6y ago
    A cubic meter of air around room temperature and pressure has mass around 1000 g, and isobaric specific heat capacity around 1 J/(g*K). So cooling that air from 30 C to 25 C requires us to suck out 5 kJ. But at 30 C and 100% RH, air holds roughly 30 g/kg of water, while at 25 C it can hold only 20 g/kg. So as we cool the air, 10 g of water will condense, releasing about 20 kJ that we also have to suck out. There's no way to cool the air without condensing the water. In my example, the "latent" heat from the water condensing was much bigger than the "sensible" heat from air cooling. In practice it seems the latent heat is typically around 25% of the total[1], since we're probably at <100% RH, and since heat probably leaks in faster than moisture does (since air leaks let in both heat and moisture, but conduction through the walls/windows lets in only heat). The latent heat would be a bigger contributor in the poorly-sealed or outdoor cooling applications that these researchers seem to be targeting. The idea of a radiant cooling tunnel appears to be old, but not very popular because it's not very effective. The cold plates leak cold into the air, just becoming a more cumbersome version of conventional air conditioning. The cold plate also can't run colder than the dew point, since the condensed water would drip and make a mess. The innovation here seems to be that they've placed a thermally non-conductive but transparent (to the thermal radiation) membrane between the cold plate and the user. There's a thin layer of cold, dry air between the cold plates and the membrane, but the membrane stops the cold from leaking out into the room air. It's analogous to the sun shining through a well-insulated window on a winter day--you still feel the radiative heating from the sun, even as the window keeps the warm and cool air separated. Normal window glass wouldn't work for the cooling case, since the heat source isn't the sun (~6000 K) but the human (~300 K), so the wavelengths are much longer, around 10 um, and window glass is opaque there. Plastics with transmission around there are known, though, like the ones used to make the Fresnel lenses for PIR motion detectors. In any case, that membrane lets them keep the cold plate colder than the dew point without condensing water onto it, and also decreases loss of cooling by convection into the air. It would work best on exposed skin. It should still work with clothes, as long as the clothes aren't too thermally insulating. 1. https://www.energy.gov/sites/prod/files/2013/12/f5/issue7_sensible_loadcontrol.pdf https://www.energy.gov/sites/prod/files/2013/12/f5/issue7_se...
m463 6y ago
Gaining or losing heat via radiation isn't as easy as conduction, but it does work. It's possible to make ice at night in temperate climates by taking the equivalent of a solar concentrator, putting water at the focus and pointing it at a dark patch of clear sky. You know, probably standing in the sun vs shade is probably the opposite analogy. In the sun you get radiative heating from the sun, in the shade you just get heating from the nearby air.
outworlder 6y ago
> but their description of cold things sucking thermal radiation doesn't jive with my freshman-physics understanding of thermodynamics. Pseudoscience alarms started to sound in my head, until I read the comments. If I understood this correctly - you will still radiate heat as normal. But, since the thermal radiation you emit will reach these things (assuming line of sight), you won't have much reflected back at you (or at nearby objects, which would heat them up). And so, you feel colder, even though the air is not being chilled. That would make sense, similar to how we can make ice during the night even in a desert. You can radiate heat into space(as not all thermal radiation will be absorbed by the air) https://tecped.com/process-of-freezing-ice-in-the-desert-according-to-physicists/ https://tecped.com/process-of-freezing-ice-in-the-desert-acc...
colechristensen 6y ago
From a freshman physics point of view, “sucking” is also not a pull-from-low process but a push-from-high process. There is some nuance there but simply, a straw doesn’t work right in a vacuum.
alacombe 6y ago
> fussing with the humidity in the air like most AC does Humidity will have to be dealt with no matter what, either by the AC system, or though condensation, as cold air holds less water vapour as warm air.

growlist 6y ago

Pretty cool (sorry)

sparker72678 6y ago

> The notoriously bad energy efficiency of air conditioners Air conditioners are actually pretty fantastically efficient for what they do. The problem with air conditioners is that there's no way to move a ton of heat without using a lot of energy. So, they do use a lot, but they make the most of it. What's truly bad are our buildings that have the minimal insulation and sealing possible, leaking all that cold air right back out into the environment.

ianai 6y ago
There’s also no obvious market factor incentivizing modernization of old RE let alone efficiency.
eggsnbacon1 6y ago
New buildings are rather efficient in US. The problem is old buildings that use 5X the energy for HVAC. I echo that AC is quite efficient. Far more efficient than traditional heating. There's a misconception that hot areas are less environmentally friendly due to AC. The opposite is true. Hot areas are only 25 freedom units hotter than humans prefer. Cold areas have months of 50+ temperature difference. The misconception persists because heat uses gas, which is 5-10X less expensive per BTU of energy than electricity. So it might be cheaper to heat cold areas than run AC in hot ones, but its much more damaging to the environment. Plus, hot climates are using a lot of renewables these days which impacts the environmental friendliness of electric but not gas. I expect migration to the sun belt to accelerate, at least in the US. It makes a lot of sense from environmental perspectives. In some southern cities there's already long stretches every summer where daytime AC use runs on 70%+ renewable energy.
- marcinzm 6y ago
  [I was wrong]
  - roywiggins 6y ago
    Air conditioners are often more than 100% efficient- they move more heat energy than they consume. (Of course if you start with a fossil fuel, turn it into electricity, and then pipe that into an AC unit, the overall efficiency will be dropped by the efficiency of the power plant, but it's still somewhat made up for by the advantages of heat pumps)

zbyte64 6y ago

I wonder how costly it is to fill your walls entirely with water pipes. Also, one currently ensures there is a stud or lack of electrical when putting nails in a wall. I guess you gotta hang things up differently.

sparker72678 6y ago
There are some "radiant cooling" installations out there. Most use either the ceiling or the floor, for the reasons you point out.
- stephen_g 6y ago
  Yeah, my brother used to work in a building that was cooled like this with a 'chilled beam' system - https://en.wikipedia.org/wiki/Chilled_beam https://en.wikipedia.org/wiki/Chilled_beam Apparently it works pretty well.
  - istjohn 6y ago
    That uses a different mechanism. It cools the air and relies on convection. TFA specifically avoids cooling the air.
alacombe 6y ago
> I wonder how costly it is to fill your walls entirely with water pipes. Pretty costly in water damages for sure, people tends to drive nails in pipes all the time already, just imagine this * 100x.

Stierlitz 6y ago

> .. as a person stands next to or beneath the panel, the body heat radiates towards the chilled panels to create a cooling sensation .. I'm not sure that is an accurate description of the physics. Maybe the air next to the panel is cooler, accounting for the cooling sensation.

yummypaint 6y ago
The cold air will contribute, but this is an accurate description. A person constantly radiates a blackbody spectrum determined by temperature, as does the surrounding room. We perceive ourselves as in equilibrium when we radiate as much as we receive. If a wall is cooler than the rest of the room, the person receives less infrared from that direction and perceives cold, even in the absence of convection.
thefiregecko 6y ago
This confused me for a bit. The point of the system is to prevent energy from being reflected or radiated from a surface. Systems like this have been around for a while (https://www.energy.gov/energysaver/home-cooling-systems/radiant-cooling https://www.energy.gov/energysaver/home-cooling-systems/radi...), the news here is that this works with temperatures below the dew point because they have solved the condensation issues.

andor 6y ago

Not sure why they are researching the mechanism, these systems are commonly installed in Germany and known as "Kühldecke" (cooling ceiling). https://de.wikipedia.org/wiki/K%C3%BChldecke https://de.wikipedia.org/wiki/K%C3%BChldecke

justinclift 6y ago
Is this the same kind of thing? (english wikipedia) https://en.wikipedia.org/wiki/Chilled_beam https://en.wikipedia.org/wiki/Chilled_beam
ladberg 6y ago
This is a bit different. A cooled ceiling cools the air through convection, but this isn't supposed to. Instead, it basically just "removes" the warm walls you'd experience in any other setting. A cooled ceiling would cool more effectively but possibly not as efficiently.
ac42 6y ago
The WP article points out the issue of condensation, which the OP claims as being addressed in a novel way.

LifeIsThermal 6y ago

Notice how the system cools by absorbing heat from a body, but the greenhouse theory says that the earth surface warms from air absorbing heat from it. The GHE is pseudo-science.

aaron695 6y ago
My new rule is upvote anyone who segues into anti-global warming statements on articles that don't mention Global Warming. Because I'm sick to death of every time an efficiency is mentioned people have to bring out their favourite religion because we all forgot about Global Warming since a hour ago. I'm also impressed you waited 3 years to comment.
ladberg 6y ago
The cooling system doesn't magically cool itself, it uses cold water to remove the heat that's added by radiation from people near it. This has nothing to do with the greenhouse effect (which occurs when you have two bodies of drastically different temperatures with an air barrier).

finphil 6y ago

This sounds promising. I wonder if such can be implemented in small dwellings.

csours 6y ago

I'm not an expert, if one is available please comment. Human perception of temperature is mostly based on 5 things: Ambient air temperature, Radiant Heat (infrared radiation), humidity, direct conduction of heat, and air movement. It seems like this addresses Radiant Heat. Another way to address this is to add more insulation, install low-emissivity windows, plant shade trees in your yard. Half of my house feels much warmer in the afternoon because it lacks shade. I used a thermometer to see the difference between the ambient air temperature in the two halves; the hot side was only 2 degrees F hotter. I don't have an IR thermometer, but I imagine that the walls in the hot side are at least 10 degrees F hotter.

username505 6y ago

This is just a geothermal unit with the evaporator built around the load and instead of air to air transfer through convection it is air to air transfer through radiation... nothing but smoke and mirrors. The problem with efficiency and A/C is the excess heat generated by the compression element of the Refrigeration Cycle. The closest thing to 100% efficiency is achieved through absorption chillers that utilize an internal chemical reaction based off of external heat to produce compression through a metered system... neat idea though. Heating systems that utilize the same process are different though - you can achieve greater than 100% efficiency with the use of flash gas bypass designs that will say for example produce 1.5 tons of heat in a 1 ton system.

ladberg 6y ago

The author doesn't really explain it well because his explanation breaks some physics laws, so it doesn't "suck" your body heat away. Instead, it lowers the amount of heat radiating onto you from your environment by replacing hot walls with cold walls, which will lower the temperature of your skin. It's efficient specifically because it doesn't cool by convection (like every other cooler). This allows the designers to insulate it so they only have to offset temperature gained by incoming heat radiation when keeping it cool. That also means it won't cool the air, just the objects near it.

labawi 6y ago
Thermal radiative coupling is bidirectional. Sucking away is appropriate and important as you do actually have to displace the energy somewhere. It works the same way when sucking air. A simpler non-radiating equivalent would be a reflective foil, or a polished metal - you could enclose yourself within it, get no radiating heat from environment, yet it wouldn't help cool you, because your radiation has no place to go.
- ladberg 6y ago
  I still feel like "sucking" is misleading because it doesn't change how much heat you radiate, only how much heat is radiated on to you. A better analogy would be like a curtains for heat.
  - ants_a 6y ago
    I think that the analogy is used because people underestimate how much heat is lost to radiation. Human body radiates energy away at about 800W. It's not noticeable, because normally it is balanced by a similar flux of thermal radiation coming in from the environment. If the apparent radiative temperature of the environment is reduced it can indeed feel like it is sucking heat out.
    - CorrectHorseBat 6y ago
      You're off by about an order of magnitude there. The human body uses ~10MJ per day which is ~100W. This not only includes radiation losses but also convection and evaporation.

OminousWeapons 6y ago

This sounds like they reinvented a swamp cooler. Am I missing something?

pengaru 6y ago
There is absolutely nothing resembling a swamp cooler going on here.

heisenzombie 6y ago

An idea I was told about relatively recently that kind of blew my mind: - Space is cold (~3K) - The atmosphere is really quite transparent in the wavelegth 8-13 μm - If one can construct an optical filter (e.g. grating) which is highly reflective except for a bandpass at 8-13μm, it is possible to reflect most solar energy but still "see" the cold of deep space - It's possible to build a box with sufficiently low thermal conduction, and this 'magic mirror' on top, to effectively refrigerate its contents by radiation to space. This uses no power, and works in direct sunlight [^1]. So weird, probably not very practical (what about cloudy days?), but very cool! [^1] in fact, if you put it in the shade then it would warm up because it could no longer radiate to space.

MengerSponge 6y ago
https://www.nature.com/articles/ncomms13729 https://www.nature.com/articles/ncomms13729
Aperocky 6y ago
Space is without temperature. Temperature is an attribute of things, space is a lack of things. What you're referring to is the temperature of cosmic background radiation, which is akin to how you emit infrared radiation at your body temperature. But you certainly don't classify the space where this radiation move through as having your body temperature. The two things are not the same imo.
- heisenzombie 6y ago
  "Temperature" is a slippery word that has many different definitions depending on what area of physics you're working in. In this case it is perfectly fine to refer to "the temperature of space" since you're explicitly using it as a cold sink. As evidence, see the paper (published in Nature no less!) that MengerSponge posted. The authors say "On the other hand, outer space, at a temperature of 3 K, provides a much colder heat sink."
  - Aperocky 6y ago
    Here's something I don't understand though, if we put a blackbody in deep space, would it eventually be cooled/heated to the temperature of the cosmic background radiation? The space around us is filled with photon coming from Sun at ~5500K, but it doesn't heat anything to anywhere near that. So given the current density of cosmic background radiation at 411 photon cm -3, would it be sufficient to place a blackbody to the equilibrium temperature? I am not a physicist by training, and this is a genuine question.

abrowne0 6y ago

This is just a regular hydronic radiant system which is very efficient because it doesn’t need to heat the air. The thing is, hydronic systems have been around for 70 years or more but they typically are not used for cooling because of the humidity issues that arise which are damaging to the building. So this can only be implemented in buildings with materials resistant to water damage. Hydronic radiant systems are the best around it terms of heating efficiency but very expensive to install. This article seems like hype and bs.

abrowne0 6y ago
It does say that there is a Novel membrane to prevent humidity build up, but there isn’t a lot of information about the membrane and what conditions it will work in. For instance, Will it work in a wooden structure with drywall?

adrianmonk 6y ago

This sounds expensive to install. For it to work as well as regular AC, wouldn't this have to be built into basically all the walls in your home?

infogulch 6y ago

This is pretty neat. It lets you (somewhat) decouple the temperature and humidity of the air from how cool it feels to be in the room, by only removing radiative heat coming from inside the room. You could choose to exchange air with the outside more rapidly without losing efficiency because you aren't putting as much energy into conditioning the air itself. I wonder if there are any infrared-transparent wall paints.

kristopolous 6y ago

I saw a very promising AC technology at CES in january that people may find interesting: https://www.oxicool.com/ https://www.oxicool.com/ I don't have the material science or chemistry background to know how effective it is, but I hope everything they claim holds water, it sounds pretty good. There's also a DIY water based AC with pipes and a cheap pump you can find widely on the internet, but I haven't done it yet. Here's an example https://www.instructables.com/id/Hollis-homemade-AC/ https://www.instructables.com/id/Hollis-homemade-AC/ ... In the comments one poster suggested a toilet tank as a reservoir, that sounds promising.

yourapostasy 6y ago
That's neat and I'm going to keep an eye on it. The -15° F ambient differential somewhat limits its usefulness, and I'd like to see an induction-powered heater as an option instead of conduction-based heating. I'm guessing the 10-year lifespan is due to the fan bearings and the molecular sieve lifetime, and I'd like to see the overall system lifespan increased by 10X. Would be interested in the papers behind this tech, as I think there are a lot of caveats they're glossing over. [1] seems to be a paper on adjacent technology. [2] seems to indicate the service lifetime of the molecular sieve is the controlling factor in the estimated lifecycle. 10 years sounds like the upper range. [1] https://aip.scitation.org/doi/abs/10.1063/1.4822041?journalCode=rse https://aip.scitation.org/doi/abs/10.1063/1.4822041?journalC... [2] http://www.yyindustry.com/news_show.asp?id=28 http://www.yyindustry.com/news_show.asp?id=28
- kristopolous 6y ago
  They're trying to get version 1 out the door. Hopefully there's a dramatic improvement and optimization curve still available given it's such early days still
leoedin 6y ago
They bury it slightly, but in the FAQ: "The primary energy for HomeCool™ is derived from clean open flame burn of natural gas. This can be converted with an optional kit to propane and also hydrogen* (*once commercially available)." It burns gas. It may work in a similar manner to absorption refrigerators often found in RVs. https://en.wikipedia.org/wiki/Absorption_refrigerator https://en.wikipedia.org/wiki/Absorption_refrigerator Burning gas isn't exactly a clean energy source. In fact, we need to be aggressively exploring ways to stop burning gas for heating - not starting to burn more for cooling!

tobyhinloopen 6y ago

Description seems like a thing from a science fiction.

b0rsuk 6y ago

Circulating fan uses tenth the energy of an air conditioner. The Revenge of the Circulating Fan https://www.lowtechmagazine.com/2014/09/circulating-fans-air-conditioning.html https://www.lowtechmagazine.com/2014/09/circulating-fans-air...