“Cold Tube” cooling system uses half the energy of an air conditioner
newatlas.com
newatlas.com
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.
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.
So some parts of construction techniques and building materials have improved significantly. However, when comparing the framing lumber used today to what was used in the 60s, I'm shocked that new construction doesn't fall over the first time the wolf huffs and puffs.
The purpose is to prevent buildup of harmful gasses and VOCs (everything from CO2 to CO to regular out-gassing of furnitures, etc) that can become dangerous if not cycled regularly.
2120: The environment is all full of poisonous gasses from the people of 2020. Each house needs its own air purifier to make the outdoor air safe to breathe.
> the first Cordis hotel on mainland China boasts something that is genuinely rare in big Chinese cities: clean indoor air.
https://www.theguardian.com/cities/2018/mar/27/china-clean-a...
That's the case in much of the world already... I live in area where there's tons of smog in the colder months and consider installing a system for bringing in filtered air from the outside, so that I won't have to open windows for the 6+ months smog period.
One reason is efficiency. In the Bay Area, it's common when the daytime high temperature is 80–90˚F for the nighttime low to be 50–60˚F. You can set your thermostat to 76˚F until sunset, then bring in outside air to cool down to 68˚F or below by sunrise. You get cool air when you're trying to sleep and avoid running the AC in the night or morning.
I'm getting my furnace & AC replaced today and was sad to learn I couldn't get one of these. The fresh air intake has to be at least 10' from the furnace flue vent, and that isn't practical with my home's design.
But there is also typically fresh air requirements to bring in some percentage of fresh air.
And lastly the HRV/ERV mentioned in the other comment is typically more a residential thing from what I've seen but that's totally a thing I want in my next house.
I was describing my home renovation project to someone who lives in Brazil. I don't how true this is for that entire country, but she said that it's very uncommon for Brazilian homes to have insulation.
I live in a modern house in Northern Europe, and we don't even turn our heating on until it gets below freezing. Because we have good insulation, only then it starts to drop below 22C (72F) inside.
...sigh. I really hope it doesn't go this way.
Hot days are getting hotter and much more frequent. Snow is getting rare. We had a yearly ice skating event that never happens anymore because there is no ice.
Weeks of 30C weather are getting more common while not long ago, hotter than 25C was considered exceptional.
It’s like daily temperatures are just shifted +5 degrees within 2 decades.
It’s not just my gut feeling, there are plenty of statistics
The whole comment is hyperbole.
- predicting what council rates (US has Land tax I think?!?) might turn into when the town realises it will be half underwater...
They can be, and there's lots of modern construction techniques that are really good (search term "building science").
One big problem is that a lot of stuff is still built to "minimum code" which just isn't that great. On top of that, sloppy construction work can significantly undermine what is done. In my own house I've fixed several simple things, like missing insulation around vents and holes cut too big (or created by a hammer, rather than cutting).
Here's a good walkthrough of a house under construction showing lots of problems typical to any subdivision (non-custom) build: https://youtu.be/OmU2N_Q732A
1,000 cubic feet of natural gas is a bit over 1 million BTU. That converts to 297 kwh of electricity.
that 1,015,000 btu costs:
$38.61 in electric
$11.85 in natural gas
(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)
> From 1990 to 2013, U.S. shipment-weighted efficiency for residential split-system A/Cs increased from 9.5 SEER (~2.2 COP) to 14.9 SEER (~3.8 COP).
https://www.energy.gov/sites/prod/files/2016/07/f33/The%20Fu...
Yes, the hot side will spit out all of the heat extracted from inside, plus the energy from the compressor operation, so indeed energy is conserved.
In the case of the house I'm currently at, it is pretty good at retaining heat in "winter" (in quotes, because it's Bay Area winter). However, in the summer it will be quite warm late at night. So sometimes I want it the other way around, I want it to radiate excess heat away as fast as possible, but I can't control that. We should be able to deploy "heatsinks" at night.
That's for a house. Modern office buildings are built like greenhouses, even when they are otherwise insulated.
We can't really roll out solar panels fast enough. They would help offsetting the cooling energy costs by a lot. After all, it's during warm sunny days where the air-conditioning needs are the greatest. They also provide shade.
Technology Connections has a good video about this: https://youtu.be/_-mBeYC2KGc?t=355
If we go by the DOE SACC ratings, this single-hose toshiba [0] has a 14% higher SACC rating than this dual hose whynter [1], for the same BTU/hr rating. If we go by the wattage ratings (note: these are usually peak rather than average), the toshiba does use 13% more power than the whynter, so let's assume it cancels out and they both have the same energy efficiency. The toshiba is still $144 cheaper than the whynter. That's hard to justify for "dual hoses seem like they should be more efficient" without any actual evidence.
Please prove me wrong, before it's too late for me to return the single-hose one.
[0] https://www.toshiba-lifestyle.com/us/Room-Air-Conditioners/P...
[1] https://www.whynter.com/product/whynter-elite-12000-btu-dual...
That air has to come from somewhere, so it's going to pull warm air from everywhere it can, door, windows, any creaks/holes/openings, etc. And the fans have some serious airflow/CFM.
Dual hose designs pull air from outside and expel it back outside.
So technically it should be capable of getting your room colder and keeping it that way with less compressor usage.
The cold part of the A/C just circulates air around the room on any model.
Looking at my model, I could turn it into a dual hose design - it pulls air from the rear, right below the exhaust vent. That seems to be the case for a lot of these. Creating an attachment/adapter to connect another hose seems easy enough.
I went years without any AC and my bedroom wall faces south. My room would get so hot in the summer I couldn't get any sleep. Tried an evaporative cooling unit because they're cheap which did absolutely nothing for me. Eventually broke down and got a portable AC which unfortunately was a single hose unit. You really need to look carefully at what you're buying because the whole single/dual tube thing doesn't seem to be something the sellers put out there. Even though it it was a single it still made a world of difference. On really hot days it doesn't get super cold but cool enough that I don't notice the heat.
The dual hose unit will likely outperform significantly if the temperature delta is high, but if the temp delta is low then the single-hose unit is probably better as it likely has a more efficient compressor.
It looks like DOE SACC tests assume the outdoor air temp is 83 degrees for 80% of your usage and 95 degrees for 20% of your usage.
In case anyone is interested, I did not end up returning my single-hose unit, but I did end up buying a dual-hose Whynter ARC-122DHP [0] for another room. It came with a yellow energy guide card listing a cooling capacity of 12000 BTUs and an EER of 11.1, which indicates an average power draw of just 1081 watts (EER=BTU/watt). Unfortunately no SACC or CEER rating was listed. Actually measuring power shows that it draws the full 1200 watts on startup, quickly drops to around 1100 watts, and then slowly drops to 900 watts as the room temperature falls. For comparison, my 8000 BTU (unknown EER, 6000 SACC, 6.5 CEER) single-hose Toshiba RAC-PD0812CRRU [1] also draws 1200 watts on startup, quickly drops to around 900 watts, and then slowly drops to 800 watts as the room temperature falls. So it seems like the dual-hose is around 20-30% more efficient (in a different room under arbitrary conditions) based off the BTU rating, but no better based off the SACC rating. I also noticed that it did not come with foam seals for the window bar like the single-hose unit did, so there is probably room for some efficiency gain there.
[0] https://www.whynter.com/product/whynter-elite-12000-btu-dual...
[1] https://www.toshiba-lifestyle.com/us/Room-Air-Conditioners/P...
Their efficiency is based on thermodynamics, so there's not much you can do to break the physical barriers.
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.
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.
This is a good analogy because (being pedantic) you can't suck air either. You can only make a region of lower pressure, into which the higher-pressure air pushes itself.
In the case of centrifugal force, it's a real thing in a rotating reference frame, but doesn't exist in an inertial reference frame (because in that frame the acceleration is towards the center, ie. centripetal).
In the case of suction, it's a real thing when your zero-pressure reference point is above 'absolute zero' pressure, such as when you're measuring gauge pressure. In this case you can have an area of 'negative pressure' which is 'sucking' the surrounding fluid into it.
The parent comment wasn't talking about net power dissipation. 800W radiation would be the case if the environment was at 0K. Usually, the environment radiates about 800W back at you.
- 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.
https://mse.umd.edu/news/story/cooling-wood-an-ecofriendly-b...
If I understand correctly, this isn't quite right. If it's in the shade, then whatever is shading it is radiating more heat onto it (because the shading object is hotter than space) and possibly reflecting its own radiated heat back. If it's under a clear sky then it's receiving less heat, so what it loses by radiating has more effect. Does that sound right?
All this system is doing is providing a readily accessible "dark corner".
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.
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."
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.
No.
As you note, in space in our vicinity there is a hot object, the Sun, in the sky, so the "temperature" of space in our vicinity is not really the 3K of the CMB, because an object placed in space in our vicinity will not come to thermal equilibrium at that temperature, but at some higher temperature. Exactly what higher temperature, if we assume the object itself is a black body, will depend on the object's surface area and its distance from the Sun.
We could, of course, theoretically place an object outside our solar system, or even outside our galaxy, or even outside our local group of galaxies, or even outside the galaxy cluster of which our local group is a part. Doing those things would move the object farther and farther, on average, from high temperature radiation sources like the Sun. But there would still be radiation from those sources in the sky, meaning that the object would still reach thermal equilibrium at some temperature higher than the 3K CMB temperature.
In short, an object would come to thermal equilibrium in space at the 3K CMB temperature only if the CMB were the only radiation source in the object's sky. But in actual fact it never will be.
The temperature of a perfect black body in earth’s orbit would be ~255K (-18C)
(This is not the case for the technology under discussion because it’s very much not a black body)
I will point out that even at modest (astronomically speaking) distances, the solid angle of a star gets preeeeetty small. For example, a black body at just 1 light year from the Sun (just a quarter of the way to Alpha Centauri) would come to an equilibrium temperature of ~1K (assuming an otherwise empty universe). So that’s already a smaller effect than the CMB.
I think in intergalactic space, the thermal equilibrium of a black body would be absolutely dominated by the CMB.
Yes, but you're not just being irradiated by a single star. There's a whole galaxy of them. They aren't all visible to the naked eye, but they're still there, and their radiation all adds up.
However, I have not done detailed calculations, so I might be overestimating, for example, what the effective radiation temperature would be of galaxies in intergalactic space.
More precisely, of a perfect black body in Earth's orbit with the same surface area and shape as Earth.
I still don't see if this answer my question, assuming CMB is the only source, but the photon density has diminished significantly, would there be enough CMB photons to keep the object from going lower than 3K from emitting blackbody radiation?
The gist of my question is: Will there ever be a time where there are not enough CMB to heat the blackbody? Just like solar photons at 5500K, there are not enough of them to heat stuff at Earth to the same temp.
Obviously not, since if the photon density has diminished significantly, the temperature of the CMB will diminish significantly too. The temperature of the CMB gets lower as the universe expands. When the CMB was originally emitted, some 300,000 years or so after the Big Bang, its temperature was around 3000K, not 3K. It has cooled to 3K because the universe has expanded by a factor of about 1000. It will continue to cool as the universe expands further.
> Will there ever be a time where there are not enough CMB to heat the blackbody?
Meaning, to heat the black body to the same temperature as the CMB at whatever time you are considering? No. The CMB is unlike all other radiation sources in that it is everywhere, and its effective temperature is the same everywhere. You can't be "at a distance" from the CMB the way you can from a star or a galaxy.
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.
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.
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.
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_se...
So I’m not seeing how much this really helps. My radiated heat shouldn’t be returning to me anyway.
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.
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.
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-acc...
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.
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/ ... In the comments one poster suggested a toilet tank as a reservoir, that sounds promising.
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?journalC...
"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
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!
A cooled ceiling would cool more effectively but possibly not as efficiently.
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.
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.
Apparently it works pretty well.
Pretty costly in water damages for sure, people tends to drive nails in pipes all the time already, just imagine this * 100x.
The Revenge of the Circulating Fan https://www.lowtechmagazine.com/2014/09/circulating-fans-air...
(sorry)
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.