Scientists Are Using the Cold of Outer Space To Rethink Air Conditioning (qz.com) 218
A California-based company called SkyCool Systems is in the early stages of manufacturing a cooling system that's more energy efficient than anything humans have used for a century. It's doing it using radiative cooling, a concept that was used in the Middle East and India hundreds of years ago. Quartz reports: To understand how radiative cooling works, forget for a moment the sun. Think instead about the night sky. Once the sun has set and the cooler evening begins, just about everything on Earth -- the soil, the grass, the roofs of homes, even people -- give off heat. A lot of that heat rises up into the atmosphere where it effectively transmits out into space, never returning to Earth. The night sky is very chilly, and objects sending heat upward at night send up more heat than the whole sky is sending back down.
Hundreds of years ago, long before refrigeration existed, people in India and Iran used this basic concept to make ice in climates with temperatures above freezing. Water was filled into large and shallow ceramic pools that were surrounded and insulated by hay, and then the pools were left out on clear nights. It sounds counterintuitive, but if the air wasn't too far above freezing, the heat emitted by the water made it lower in temperature than the surrounding air, allowing it to freeze. It's the same principle at play when you wake up on a summer morning to find a layer of frost or dew. Now the people at SkyCool are taking that principle and applying it to the modern era, employing it to reimagine how we cool our homes, data centers, and refrigerators. SkyCool's three co-founders created a material that helps facilitate the radiative cooling process.
"Their invention looks a lot like a solar panel," reports Quartz. "A flat metal panel is covered in a sheet of the material -- a high-tech film -- the trio invented. The material reflects the light and heat of the sun so effectively that the temperature beneath the film can drop 5 to 10-degrees Celsius (41 to 50-degrees Fahrenheit) lower than the air around it. A system of small pipes circulating through the metal panel beneath the film are exposed to that colder temperature, cooling the fluid inside before it's sent out to current-day refrigeration systems." A new study published today in the journal Nature Sustainability says radiative cooling could one day be its own, electricity-free system.
Hundreds of years ago, long before refrigeration existed, people in India and Iran used this basic concept to make ice in climates with temperatures above freezing. Water was filled into large and shallow ceramic pools that were surrounded and insulated by hay, and then the pools were left out on clear nights. It sounds counterintuitive, but if the air wasn't too far above freezing, the heat emitted by the water made it lower in temperature than the surrounding air, allowing it to freeze. It's the same principle at play when you wake up on a summer morning to find a layer of frost or dew. Now the people at SkyCool are taking that principle and applying it to the modern era, employing it to reimagine how we cool our homes, data centers, and refrigerators. SkyCool's three co-founders created a material that helps facilitate the radiative cooling process.
"Their invention looks a lot like a solar panel," reports Quartz. "A flat metal panel is covered in a sheet of the material -- a high-tech film -- the trio invented. The material reflects the light and heat of the sun so effectively that the temperature beneath the film can drop 5 to 10-degrees Celsius (41 to 50-degrees Fahrenheit) lower than the air around it. A system of small pipes circulating through the metal panel beneath the film are exposed to that colder temperature, cooling the fluid inside before it's sent out to current-day refrigeration systems." A new study published today in the journal Nature Sustainability says radiative cooling could one day be its own, electricity-free system.
Incorrect unit conversion (Score:5, Insightful)
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Ok, so its saying if it is 98F out, it will cool my house to 80F working at maximum.
That's still too freakin' hot on a muggy day out.
Call me back when it can cool to 74-75F during the day sustained at minimum.
It might be ok for evening, to get it to 72F so I can sleep, but 80F indoors during the middle of the day is very uncomfortable.
Especially in the high humidity down here.
Hell, as it is now, my AC clicks on full time about mid A
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"cooling the fluid inside before it's sent out to current-day refrigeration systems"
It sounds like this is meant to be used in concert with your normal air conditioner, giving it a boost in effectiveness and efficiency.
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The water temperature is still higher than the target air temperature of the house.
And? So is outside air when you're chilling with an air-chilled AC radiator. The refrigerant pipes circulating through this water would contain compressed refrigerant - which contains a lot more heat density. Getting the refrigerant to this temperature is going to be way better at cooling once you expand the refrigerant and run it through the indoor coil.
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Or, it could be used exclusively on days where the temperature only gets up to 90F. Then, the unit required to drop the temperature to 70F would be much smaller. So, you would have this system connected to a much smaller AC unit.
To make it more efficient, the coolant could be pumped to a large underground tank, and the system could run throughout the night. Dropping the temp of a large water tank down to 50F would provide HUGE heat sink for the heat of the day. On the hottest days here in NC, you can ex
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It's misunderstood and misleading information... (Score:2)
That's why it doesn't make sense.
Then again, they did jam "SPAYSE!!!" in there trying to win the buzzword bingo, along with "for centuries", "sky" and "renewable", so it's kinda by design.
It doesn't cool at all. It's a very special kind of mirror.
I.e. It reflects the sunlight at near- and mid-infrared frequencies, thus creating a temperature gradient with the surrounding area, while it is exposed to the sun.
Put it in the shade... nothing happens.
I.e. It doesn't work at night.
Cooling with SPAYSE!!! is becaus
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I didn't see the conversion problem in any of TFAs but this was in the second link on quartz.
The material reflects the light and heat of the sun so effectively that the temperature beneath the film can drop 5 to 10-degrees Celsius (9 to 18-degrees Fahrenheit)
50 Degrees Fahrenheit? (Score:4, Insightful)
Err, a 5 to 10 degree change in Celsius would be a 9-18 degree change in Fahrenheit. If only there were some kind of device that let people easily do mathematical operations...
Re:50 Degrees Fahrenheit? (Score:5, Insightful)
Re:50 Degrees Fahrenheit? (Score:5, Insightful)
Maybe there's still some hope for Slashdot as a news for nerds site.
Maybe there's still some hope that the US will finally abandon archaic imperial units, and finally shift to the metric system.
Otherwise, somebody somewhere will inevitably make a conversion error, and it might have fatal consequences.
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Maybe there's still some hope that the US will finally abandon archaic imperial units, and finally shift to the metric system.
We don't use imperial units or SI, being neither a colony of the UK nor France. We use US units. For us, a hundredweight is 100 pounds, and thus a ton is 2000. The British Empire had its "long hundredweights" and "long tons", best forgotten.
Admittedly, SI took the same notion of rationalizing units a step further, making the furlong a round 200 meters instead of 220 yards, but then they messed it all up with "hectairs", instead of just calling an acre 200x20 meters like sensible people.
The US system is m
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Lessee here.... 0.357 inches... little bigger than a third of an inch.... that's gotta be 'bout 9mm don'tcha think?
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The UK uses metric - it's part of Europe. Gas is sold in litres. Temperatures in The Guardian are given in Celcius. Some things are reported in both, but legally it's metric that is the standard. Same as Canada, you can buy stuff labeled in both kg and lb, but in case of disagreement between the two, metric is authoritative.
There are only two shitholes and one country in decline that don't use metric - Liberia, Myanmar, and the USA.
95% of the world has moved forward to metric. It avoids conversion error
Re:50 Degrees Fahrenheit? (Score:5, Insightful)
Road signs in the UK, and therefore speedometers/odometers on vehicles, are measure distance in miles. People colloquially give their weight in stone, an archaic unit equal to 14 lbs. Beverages are, famously, sold in pints.
Presumably that's what OP was referring to by "not fully on metric."
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"We have declared this idea to be the best, and if you stupid morons don't use it then you're all a bunch of fools"
-Best way ever to not get something done.
I remember in elementary school, the teacher using a similar method on teaching the metric system: how backward we were for not using it, how stupid inches were, etc.
I also remember thinking "Just to spite you, you old hag, I won't use metric".
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95% of the world has moved forward to metric. It avoids conversion errors like the Mars probe and the Gimli Glider.
Um, except neither of those things would've happened if metric hadn't been invented. Particularly the latter, which IIRC happened during the changeover period and was the result of arithmetic error in the conversion formula.
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Using his provided conversion of course
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So here we go again (Score:5, Informative)
More publicly funded university research that the researchers are turning into a company and intending to sell for a profit to us - the people who completely paid for its development (as well as their salaries).
Re:So here we go again (Score:5, Interesting)
No, you didn't "completely [pay] for its development (as well as their salaries)." Federal funding of research has been declining for decades [sciencemag.org], and the entire point of the Bayh Dole Act [wikipedia.org] was to further extract the government from funding research programs. They are now funded by a mixture of government funding, private sponsored research agreements, technology development office income, and yes, student tuition (especially salaries for the latter). University technology development offices are expressly charged with making money from basic research to fund future basic research.
You want to pay pennies on the dollar yet claim the results. That's even before reaching the problem that research labs do not turn out commercial grade products, and private entities are the only ones doing the engineering and commercialization that produce those products -- typically while paying royalties back to to the University.
Well, you can't. Completely pay for something's development, or shut the hell up. You can't even support college education state support at levels of decade ago [pbs.org], much less what your parents had [npr.org]. Try paying for that before claiming that you've "completely paid" for anything, because you haven't. Not even close.
Re:So here we go again (Score:4, Interesting)
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Why would you want that?
100% taxpayer funded, no patents allowed:
In this case the government curates all university R&D funding. yuck. Even worse, commercial companies thwart university research since the results could not be patented. Even worse yet, if the results are not patented all that US government spending goes right to foreign companies.
0% taxpayer funded, private patents allowed:
Corporations curate all university R&D funding. No incentive for pure research since commercial companies wo
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If you'd actually read the links that I posed, you'll find that it is not. For example, the word "staff" is mentioned once: "Officials at the university complained to their Senator, Birch Bayh, whose staff investigated."
But thanks for your attempt to hijack my sources to say something completely different. Now we can safely ignore
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No, they don't come out and say as much. But it's implied and the data shows it. If you look at the numbers, you'll see that the spending per student has fallen by around $800/year while the cost to the student has increased by dramatically more (numbers adjusted for inflation). If state funding cuts were to blame, we would see the cost to the student rise by the exact amount of the funding cut.
Look, my only "day job" was working at a university. They were dramatically overstaffed in the early 90s. I j
Oh Goody, I get to bring (Score:3)
Yes, the title doesn't directly pertain to your point, the data does. Also, football is profitable and there's damn little [ed.gov] in the way of women's studies and diversity. 70% of degrees are business, law or STEM. If you're willing to include teachers in that you'll get it to 75%. If you're willing to include communication (read: the marketing drones that sell the crap us techies make) you'll get the number of useful degrees into the high 80s.
No, there isn't nearly as much waste as everyon
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Yeah, no.
I graduated in 1994, lived in a ratty dorm built in the early sixties, scraped by for food.
I go by my PUBLIC university now: Big beautiful resort style accommodations, giant food courts with food from all over the world, and cafeterias with meal plans offering restaurant style dining.
Enormous fully stocked gym replacing a grassy soccer field that once existed there. Tier upon tier of parking paid for by hefty quarterly fees where once we either spent ages driving around looking for a spot, or simpl
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State Universities:
In 1975 a student was responsible for approximately 20% of the actual cost of their tuition, meaning
- you could actually work a minimum wage job and put yourself through school at the same time (I did this)
- you did not need to pile up huge loans that you would be paying back for the next 20+ years
Today the student is responsible for 90%+ of the actual cost of their tuition, meaning
- with the meager increase in minimum a student cannot put themself through school working a minimum wage jo
Stanford is a private university (Score:4, Interesting)
More publicly funded university research that the researchers are turning into a company and intending to sell for a profit to us - the people who completely paid for its development (as well as their salaries).
A) Last I checked Stanford (where the research was done) is a private university, not a publicly funded one
B) You have cited no data indicating funding for the research on this came from a dime of taxpayer dollars
C) Even if they did receive public funding, so what? If they can turn it into a business good for them. Not like you were going to do it.
It will (hopefully) create jobs and tax revenue (even if not publicly funded) and patents (public data on how it works) so what exactly are you bitching about? Taxpayers will get their money back multi-fold if this turns into a successful enterprise via tax revenue. You think the data should just be thrown out there to rot? Or maybe you think you should be the one to get to build a business off their work even though you haven't lifted a finger.
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Or maybe you think you should be the one to get to build a business off their work even though you haven't lifted a finger.
Uh, isn't this basically what every major corporation does already? Why is it ok for a private citizen or corporation to expect to reap the rewards of someone's labor simply because they paid for it, but if we citizens expect the public to reap the rewards for labor that was paid for by taxes then suddenly that is bad?
Buy research to get economic growth (Score:2)
Why is it ok for a private citizen or corporation to expect to reap the rewards of someone's labor simply because they paid for it, but if we citizens expect the public to reap the rewards for labor that was paid for by taxes then suddenly that is bad?
We do reap the rewards for publicly funded research. We pay tax dollars which are then used to fund research which then results in businesses which means jobs. In fact we collectively get back many times the amount we pay in tax dollars in economic growth. Scientific research is the engine of a strong economy. If you pay indirectly for something you should expect an indirect payback which is EXACTLY what we the taxpayers get. We buy research to (eventually) get economic growth and it's a good investmen
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We pay tax dollars which are then used to fund research which then results in businesses which means jobs
You misspelled "which means privilege to create profit for your betters you filthy pleb".
In fact we collectively get back many times the amount we pay in tax dollars in economic growth.
There you go again... What's wrong with you? Is is some kind of a brain disease?
You keep typing variations of "profit for your betters you filthy pleb" wrong.
We buy research to (eventually) get economic growth and it's a good investment in general.
AND AGAIN!
You really should have that looked at by your local brain professional.
Now you misspelled "profit for our betters you filthy pleb".
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A) Standord is a private university, not a publicly funded one
Just to clarify: Just putting "private" in front of something doesn't mean government funding isn't involved. You can bet that the researchers apply for every grant possible, government or private. It's really a mix.
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Ideas are a dime a dozen. The real work is in bringing an idea to fruition.
Most university research, like the research that spawned this, comes up with a principle or an idea. Now someone is doing to work, at no cost to you, to create a real product from that idea. It might work out and lead to profit. It might not, and lead to losses. Someone else, not the taxpayers, is shouldering that risk.
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That isn't capitalism. It is the merger of corporations and the state, corporatism, or as Mussolini would call it "fascism".
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Don't confuse the free market with capitalism. Capitalist is just interested in using their capital to create more, and buying government is one way to do it. Society is interested in a free market with regulations to keep the capitalist in check.
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Anyone who suggests doing something about it is extreme. Anyone who puts it out in too much detail is paranoid and crazy. Credibility is the only currency that matters and the system is rigged in such a manner that anyone who opposes it automatically has no credibility.
Echoes of Asimov (Score:5, Interesting)
I'm reminded of a passage from "Prelude to Foundation":
No city so vast was ever recycled so tightly. No planet in the Galaxy had ever made so much use of solar power or went to such extremes to rid itself of waste heat. Glittering radiators stretched up into the thin upper atmosphere upon the nightside and were withdrawn into the metal city on the dayside. As the planet turned, the radiators rose as night progressively fell around the world and sank as day progressively broke. So Trantor always had an artificial asymmetry that was almost its symbol.
Re:Echoes of Asimov (Score:5, Interesting)
For me the 'radiative cooling' reminded me of another Asimov book: The fantastic Voyage, destination brain II
In it a scientist describes the air conditioning system of their vessel with which they are about to enter the blood steam of a living person. It is described as particles that capture the heat and then get radiated into space,...
Sounds fishy (Score:4, Interesting)
A few years ago, there were companies that sprung up to take advantage of federal tax rebates on solar by selling snake oil "solar" air conditioners. The gist of how it worked looked very similar to this - the hot refrigerant gas from the compressor was piped into an evacuated tube solar collector (ostensibly to add more heat to the refrigerant, which is actually counterintuitive to improving efficiency if you understand how the carnot cycle works), before continuing its journey to the condenser coil. Independent testing revealed these systems didn't save any energy at all.
The companies pushing these things were also rather aggressive in defending their products against anyone calling them out on their bullshit. As near as I can tell, I think most of them got sued [kuam.com] out of existence for running a scam.
I just can't help but think this looks like the exact same system, now with a thermodynamically valid technobabble explanation for how it supposedly operates. If it really were possible to radiate heat into space with the blazing hot sun beating down on your radiator, this could technically work. Until I start seeing the independent testing results though, I'll remain skeptical.
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If it really were possible to radiate heat into space with the blazing hot sun beating down on your radiator, this could technically work.
Err, I think it only works at night.
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Now if you point it straight up at the night sky, the heat radiated by the object at the focal point is all going towards the sky, so it radiates off at least twice more quickly than if it was simply laying on th
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I think it only works at night.
I think it only works on a clear night. It's fine in Iran, or maybe in California, but won't do much good under a cover of clouds.
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When there are clouds, the material will indeed still emit radiation, causing it to cool down. But at the same time the material will also receive radiation from the clouds, causing it to heat up. The resulting equilibrium temperature will be significantly higher when there are clouds.
The same effect can be seen on cars parked outside in cool weather: after a clear night the chance of ice deposit on the windows is much larger than on cloudy nights. And cars under a carport, even if completely open except fo
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Assuming their special "high-tech film" is just a mirror, then there is no reason to think it'll fail to work under clouds.
It will fail to work. They're not describing cooling via radiation with their retarded ancient Indian technique example. They're describing evaporative cooling. That only works when it's dry.
And what they're actually doing is running heatpipes to a heatsink and putting it in the shade by layering an expensive film on it. It would be more effective to just put it in actual shade.
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The temperature of the heat sink doesn't really matter that much... that's just fodder for the journalists. What matters is what frequencies of IR radiation you are receiving back from the environment. If the environment is mostly radiating back at you at frequencies which your selective mirror reflects, you're good to go... so long as you material also has the capability of up/down converting its internal phonons into a frequency of photon that can escape its own surface.
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"The core thing the material does is make this effect useful during the day," Raman says. "Most materials absorb enough sunlight to totally counteract the cooling effect. That's been the big issue. You couldn't do it during the day, when you need cooling the most."
Maybe stick it in the shade? The big issue is that radiating heat is the dumbest and worst way to remove heat. If you want to get rid of heat in space you use a heatsink and transfer heat to it (typically via conduction) then you jettison the fucking heatsink. If you have an atmosphere to dump heat into, you use convection to cool your heatsink.
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The summary seems to suggest that this is AC for use at night. Maybe the idea is to cool a large heatsink overnight and use it to cool air during the day? (Or, more likely, the summary is rather unhelpful).
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I don't know about this particular product but there are similar materials which also work during the day, in full sunlight. The trick is to bounce back every color of light except the color which your material is specially engineered to emit as black body radiation, and to choose that color of light optimally so you receive less of it from the sun/environment than you emit.
Re:Sounds fishy (Score:5, Interesting)
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https://arstechnica.com/scienc... [arstechnica.com]
The sugars in cellulose are effective emitters of infrared radiation, and they do so in two areas of the spectrum where none of our atmospheric gases is able to reabsorb it. The end result is that, if the treated wood absorbs some of the heat of a structure, wood can radiate it away so that it leaves the planet entirely.
Because of thermodynamics, something that is good at emitting radiation is also good at absorbing it, and anything good at reflecting is poor at emitting. If you placed a normal mirror over an object, it would cast a shade and reflect additional incoming light, but it would absorb and emit or reflect IR back at the object. So normally a mirror would make for a good insulator, but would not cool an object. Because these special mirrors can
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Independent testing results like this [arstechnica.com]? Different material, same concept.
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Independent testing results like this? [arstechnica.com] Different material, same concept.
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Oh, so you're not questioning that the thermodynamics could work at all, eh?
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It's not snake oil - vapor adsorption refrigeration is a legitimate thing and it runs off heat. Read up on some 'technobabble' below:
https://en.wikipedia.org/wiki/... [wikipedia.org]
That said, it's far less efficient than the 'normal' vapor compression cycle. But welcome to the "benefit" of green rebates.
As for radiating heat, heat pumps aside even, one would typically put an IR radiator in the shade to avoid that "blazing hot sun" ... but what do I know.
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When I was in high school, in history class, we read was that ice production like what the summary described relied on over night winds to chill the water below freezing. I proposed a test of this theory. A few of my classmates and I designed and built setups similar to what the summary described, with one shielded from the wind but still open to the night sky.
Though our experiment didn't produce any ice, the water exposed to the wind did cool a few degrees below the over night ambient low, while the water
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Just use a heatsink without the magic film they're selling you. Build an awning over it so it's in the shade but still exposed to the atmosphere.
Bam, free cooling. If you want to cool below ambient, you use gas expansion and heat pipes to move that shit. No special film required. Radiating heat is the worst way to move it away. Paying for a system which tries to maximize radiated heat is retarded.
Further, if their system works at all you then have to deal with cooling your heatsink below ambient, becau
This is pretty simple thermodynamics. (Score:3)
If you start a heat transfer, the rate of energy transport is proportional to the temperature difference.
If the temperature changes, the rate of change of the heat transport lags, transferring faster than the current rate, and can make the temperature of the mass go below the ambient temperature, due to the rate of transport being non-zero, even though there's no temperature difference at the current instant.
I see this on my computer, when testing new heatsink combos; there's a dip below ambient after the processor stops generating 150 or so watts, and returns to making 50 watts as the test ends.
The heat flow flow maintains the higher level for a short while, due to the flow of heat from the rapidly cooling processor mass continuing for a bit.
It's apparently proportional to the mass of the cooled object, as a huge mass of copper will do this more so than a small heat pipe heatsink.
I could see freezing, or at least cooling a pool of water, even without the evaporative effect, which would be sealed off by this IR transmissive film.
A simple 'space blanket should work; a large cooler should be enough mass. I think I'll set it up with a thermocouple and see. :)
Re:This is pretty simple thermodynamics. (Score:5, Informative)
If you start a heat transfer, the rate of energy transport is proportional to the temperature difference.
That is for conduction.
For radiative heat exchange, the rate is proportion to the difference in the FOURTH POWER of the absolute temperatures.
Stefan-Boltzmann Law [wikipedia.org]
So even small increases or decreases in temperature can make a big difference.
I give this summary a C (Score:5, Funny)
I give this summary a C, which is 4 to 6 alphabets lower than a B.
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This is the second article I have read today making the same error. That is about one article in Celsius. (Both on different nerd-sites about different subjects...)
Desiccant based A/C (Score:5, Interesting)
Somewhat off topic, but there's a YT channel where this guy has put together a homebrew desiccant based A/C system that's 3 - 5 times as efficient, compared to typical compressors with refrigerants as working fluids (standard A/C). I don't think the OP article here is directly related to that. But it's interesting. And shows there are still efficiency gains to be had in architectural cooling.
https://www.youtube.com/watch?... [youtube.com]
Comment removed (Score:5, Informative)
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He responds to that criticism in the video here:
https://youtu.be/R_g4nT4a28U?t... [youtu.be]
In the demonstration system, he uses an alcohol heater. But he points out there are multiple ways to generate that heat, including solar thermal directly (or photovoltaic). Further, he argues the difference between total thermal efficiency of the system versus COP. But that's a debate between you and him. Not me. Which is why I linked to the secti
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The question is, can you scale growing your own fuel up to a whole population? If so, maybe it would be more efficient for people to drive Mustangs with their own moonshine fuel than to drive a Prius. Though, that presumes the Prius can't burn the moonshine. Because if it could, then it would once again be more efficient than the Mustang, per unit fuel.
Regardless, the engineer made a point about efficiency that hasn't been refuted here. Because even considering pure energy efficiency and not cost efficiency
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I've seen this, and I think the conclusion here is that the guy just made something massively large and hasn't shown a video of the thing actually being saturated.
Amazing temperature drop (Score:2)
Al Gore wants his tubes back (Score:2)
A system of small pipes circulating through the metal panel beneath the film
They invented an air conditioner that works like the internets. Cool.
Shadows (Score:2)
I think the scientists just discovered that things are cooler in the shade.
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I think the scientists just discovered that things are cooler in the shade.
This comment just demonstrates you didn't watch the video, it actually gets cooler when taken out of the shade. In shade it can only dump the heat into the shade tree, or whatever is blocking the sun, but out of the shade it can dump heat into the much colder outer space. This is very cool technology, if you pardon the pun. One big problem solar PV panels have is staying cool as the heat reduces efficiency. If they can make this cheap enough then it can reduce the cost per watt of PV cells.
Radiant Barriers (Score:3)
Radiant Barriers have been around for a long time. They may have invented a better version but this has been a thing forever. You can buy the panels at Home Depot. The problem is that in places like southern Arizona, 10-20 degrees isn't going to cut it. They're not a sufficient solution. They can help increase the efficiency of existing A/C systems by reducing the initial amount of heat, but you've still got 10-20 degrees or more to go.
The cost savings is around 5-10% with existing panels.
https://www.azcentral.com/stor... [azcentral.com]
It can take decades to recoup the cost of installation. If it's put in on a new build, it might make sense. But for most people, better insulation is a better idea. It really doesn't matter how hot the attic is if it doesn't come through to the living areas.
Okay, this sounds cool (see what I did there?) (Score:2)
But in all seriousness, it sounds like they've discovered that...it's cooler in the shade than it is in direct sunlight. I live in the south, and during the summer the prime parking spots aren't near the door, they're under a tree or anything that might provide some shade.
Maybe I'm missing something?
Put the heat exchanger underneath a solar panel (Score:2)
What's the actual ehat rejection power? (Score:3)
All I'm seeing is reference to temperatures; that's not sufficient to do anything with. How much power can these things reject per unit area?
Say a small single room AC unit can remove about 0.75 tons (9000 BTU/Hr or 2.64KW) of energy from a room. Let's also say it's a really efficient unit with an EER of 12.0 (which is good for such a small unit) meaning the ratio of BTU/Hr moves to energy consumed in watts is 12.0:
EER = 12.0 = 9000 (BTU/Hr) / Watts --> Watts = 750
Add that to the 2,640 watts it's removing from the room, and you need to reject 3,390 watts in total to the environment.
How much radiative cooling can be achieved is difficult to pin down; one source I found [aceee.org] pans out to roughly 100 watts per square meter. Another [aceee.org] estimates 15.9 BTU/Hr per square foot (just 50 watts per square meter).
So going by the more optimistic 100 w/m^2 we'll "only" need ~340 square meters of panels to keep one small room air conditioned.
Now maybe their engineered material performs significantly better than the metal roofs cited in those studies. Even if it's ten times better, you still need a radiative surface area roughly double the size of the room it's cooling (based on rule of thumb for sizing domestic AC units). Even if the effectiveness is double that again because you're pushing the heat into it (panels are warm/hot to the touch) you're still on par with floor area.
This certainly has a place in the grand scheme of things but I'm not holding my breath this will see widespread adoption in the HVAC/refrigeration world.
=Smidge=
Romans, too (Score:2)
The Roman troops occupying Carthage used that method to make "ice cream" (probably really sherbet). But you didn't catch them using that method in Italy.
That method works well where night skies are clear. It's lousy if it's cloudy. Use it in a desert and it will work well. Other places...not so well. Places that are cloudy or rainy, forget it.
So it could be a great supplement (or perhaps replacement) for air conditioning in a desert environment, especially is you had a room used as an "ice chest", and
farce - and idiot conversion (Score:2)
moron writing summary put 5 to 10 degree C drop in as absolute C temperatures and converted to F! hahaha
no, this is for drop of 9/5 of 5 to 10 degrees C....9 to 18 degree F lower.
Yeah and 18 degree drop is investor marketing spew dream case.
this thing won't work when its mid 80s or higher... like right now.
Good to see it gettig deployed, but ... (Score:5, Informative)
I have been looking at this technology since about when these guys published. (Was looking for better ways to air condition my house on the Nevada high desert.)
This is the Stanford team. They came up with the idea and made it work. Their approach uses a nanotech composite pigment - pricey to make initially. (I hope they were able to bring it down.) It does the whole job: radiating sharply in the infrared window, reflecting the rest. They got about 5C drop in sunlight. (I'm guessing it's because they don't cut off soon enough at the top of the IR window and so still soak up a bit of light.)
It's good to see them getting a product out. They came up with this and deserve rewards, big time.
Having seen this, some material science guys at U Colorado realized that the stuff was basically a resonator. They were working with micron scale glass beads as resonators. So they came up with their own, cheaper, way to do it.
They used 8 micron beads - six percent by weight - embedded (randomly, by mixing it into the resin then drawing it into a film) in TPX plastic (an infrared-transparent plastic that is very stable in sunlight - though they say you could do almost as well with other, less durable but common and cheaper, plastics). The result radiates in the window but transmits elsewhere, so they aluminized the back surface.
Theirs gets 10C temperature drop in direct sunlight. It's easily manufactured in a roll-to-roll process, so it would cost about 50 cents per square meter.
It gets about 93 watts of heat-dumping per square meter (I haven't seen the numbers on the Stanford guys' stuff but with half the temp drop I'd guess it might be half that. Sticking with the glass beads for now ...) My cheap air conditioner has a COP of a bit over 11, so that's about 8 watts of line electricity per square meter of helper cooling panel on the hot side. So you'd need something like ten square meters of panel to boost a small room air conditioner.
If you could do this in a paint it would cool the building surface 24/7 (good for hot-all-year climates.) The Stanford pigment would work. The glass beads too, if you did a two-layer paint job. (Though I'd worry about them being an inhalation hazard.)
Somebody came up with another way to do this in a paint: It's an oil-based paint with water added, mixed so the water forms microspheres when it's applied and curing. After a few days the water evaporates out through the paint, leaving voids that do the same resonant just-the-infrared-window trick. Haven't see how well this works, but it's already commercially available.
But REAL good for solar panels. (Score:3)
The glass beads, being transparent at other frequencies and resonating below even the 1130 nm bandgap of silicaon (so they won't absorb anything useful for a solar panel) also have a great potential as a cheap coating on solar panels. Panels work better when they're cooler, so applying them can be profitable by boosting the panel output.
One thing that had troubled me about solar energy in the "fix global warming' scenario is that solar panels absorb about all that htis them. What doesn't end up as power -
Global warming (Score:2)
Could this be used to fight global warming? Not just by dropping electricity usage, but by radiating more heat back into space? If the material converts heat to a wavelength that isn't absorbed by the atmosphere, how much would it take to counteract the heating caused by CO2?
With all the scaremongering about how we're all going to die if we don't elect a radical leftist as President, it would seem that painting roofs would be a first step to get the heat out.
This can't cover the entire Earth. Granted. B
BULLSHIT (Score:2)
A California-based company
Red flag number 1.
called SkyCool Systems
Red flag number 2. The name is generic as fuck but still tries to seem hip.
is in the early stages
Red flag number 2. They have nothing to show.
of manufacturing a cooling system that's more energy efficient than anything humans have used for a century.
Red flag number 4. They instantly jump to a claim of being revolutionary.
It's doing it using radiative cooling, a concept that was used in the Middle East and India hundreds of years ago.
Red flag number 5. They're unlocking the ancient secrets of exotic lands.
Quartz reports:
To understand how radiative cooling works, forget for a moment the sun. Think instead about the night sky. Once the sun has set and the cooler evening begins, just about everything on Earth -- the soil, the grass, the roofs of homes, even people -- give off heat. A lot of that heat rises up into the atmosphere where it effectively transmits out into space, never returning to Earth. The night sky is very chilly, and objects sending heat upward at night send up more heat than the whole sky is sending back down.
Red flag number 6. Taking a basic concept - things cool off at night - and pitching it to moronic investors.
Hundreds of years ago, long before refrigeration existed, people in India and Iran used this basic concept to make ice in climates with temperatures above freezing. Water was filled into large and shallow ceramic pools that were surrounded and insulated by hay, and then the pools were left out on clear nights.
Red flag number 7. They're taking that concept and totally misapplying it. Water can freeze in a range of ambient
Combo pack? (Score:2)
So, do they use this efficient reflector to concentrate the light on a separate solar electric system (heat or photo-voltaic) system, for a double-whammy?
Re: (Score:3)
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It's actually incredibly efficient, once you have it... for the given intents and purposes, pretty much free. The question is, since it provides only a small difference in temperature which only pre-cools or handles low-level cooling needs, is it worth the material it takes to construct and the space it takes up? That'll be a yes in some situations and a no in others, with more yes if the specialized material cost and cost of its distribution and application, including externalized costs, is brought very
Re: (Score:2)
Then article states that the device can drop air to a temperature significantly below ambient. How would it perform if a liquid much higher than ambient were pumped through it?
My AC currently has the radiator that the hot, liquified gas is pumped through, and a fan promotes convection to pull the heat out. Radiative cooling is a very small component of the heat shedding. Would this material drop the temperature of the fluid further, and without the use of the fan?
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I'm not a solid state physicist, but the hotter you get the material, the more it will radiate, and I haven't seen any mention of a limit on radiation within the bandgap.
(They do like to radiate towards the sky because there is less radiation inside the bandgap incident from that direction, so a window AC might not be optimal)
However, when you get a black body much hotter than the surrounding environment, it can pump out radiation on all IR frequencies at a much higher rate than it is incoming. This might
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Are you retarded? Yes, you are.
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I don't understand why they don't sell panels that I can make an awning for my deck out of. Sitting outside in the summer can be miserable here. With this coating I could shade the deck and be more comfortable.
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They do. https://www.sunsetter.com/ [sunsetter.com]
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Given the likely installation cost, yes.
Skycool.com.au sells a similar solution as roof paint though, that's economically attractive simply to save on electricity costs. Even with ground water to air heatpumps.
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3. You use a geothermal transfer medium (probably something circulating-water-based) as the heat dump for the A/C unit instead of the atmosphere.
I haven't bothered doing any physics, but having a 55F place to dump the heat instead of blowing a lot of 90F air through the compressor may improve efficiency.
(Also, I'm wondering how that poster proposes to heat a house to ~70F with something that's 55F.)
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I think the ultimate source may be at https://techxplore.com/news/20... [techxplore.com] And, yes, it's mostly BS I think. Radiative cooling can work and was used in times past to make ice on near freezing nights in desert areas of Iran and India. But I'm having trouble figuring out how their proposed "system" -- a bunch of 40 cm high 25 cm on a side boxes covered with a magic polymer film can generate more than token cooling. IIRC solar radiation has a large IR component. That's why solar hot water which uses IR is mu