'Electrocaloric' Heat Pump Could Transform Air Conditioning (nature.com) 160
The use of environmentally damaging gases in air conditioners and refrigerators could become redundant if a new kind of heat pump lives up to its promise. A prototype, described in a study published last week in Science, uses electric fields and a special ceramic instead of alternately vaporizing a refrigerant fluid and condensing it with a compressor to warm or cool air. From a report: The technology combines a number of existing techniques and has "superlative performance," says Neil Mathur, a materials scientist at the University of Cambridge, UK. Emmanuel Defay, a materials scientist at the Luxembourg Institute of Science and Technology in Belvaux, and his collaborators built their experimental device out of a ceramic with a strong electrocaloric effect. Materials that exhibit this effect heat up when exposed to electric fields.
In an electrocaloric material, the atoms have an electric polarization -- a slight imbalance in their distribution of electrons, which gives these atoms a 'plus' and a 'minus' pole. When the material is left alone, the polarization of these atoms continuously swivels around in random directions. But when the material is exposed to an electric field, all the electrostatic poles suddenly align, like hair combed in one direction. This transition from disorder to order means that the electrons' entropy -- physicists' way of measuring disorder -- suddenly drops, Defay explains. But the laws of thermodynamics say that the total entropy of a system can never decline, so if it falls somewhere it must increase somewhere else. "The only possibility for the material to get rid of this extra mess is to pour it into the lattice" of its crystal structure, he says. That extra disorder means that the atoms themselves start vibrating faster, resulting in a rise in temperature.
In an electrocaloric material, the atoms have an electric polarization -- a slight imbalance in their distribution of electrons, which gives these atoms a 'plus' and a 'minus' pole. When the material is left alone, the polarization of these atoms continuously swivels around in random directions. But when the material is exposed to an electric field, all the electrostatic poles suddenly align, like hair combed in one direction. This transition from disorder to order means that the electrons' entropy -- physicists' way of measuring disorder -- suddenly drops, Defay explains. But the laws of thermodynamics say that the total entropy of a system can never decline, so if it falls somewhere it must increase somewhere else. "The only possibility for the material to get rid of this extra mess is to pour it into the lattice" of its crystal structure, he says. That extra disorder means that the atoms themselves start vibrating faster, resulting in a rise in temperature.
When I hear "Air Conditioning", I think COLDER... (Score:2)
When I hear the words "air conditioning" I automatically think cooling things off.
I know conditioning the air techni
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I really need new glasses...
I really DON'T have a problem staying warm....
It is the staying cool that is the problem.
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64% Carnot efficiency is really good too! Power density looks reasonable as well.
Hopefully this survives the migration out of the lab. Could change cooling. Efficiency of a compression-based cooler with the convenience of peltier coolers.
Re:When I hear "Air Conditioning", I think COLDER. (Score:5, Interesting)
You can convert energy to heat, but it turns out to be exceptionally difficult to go the other way.
Outside of labs it basically is never done.
You're overlooking thermocouples [wikipedia.org], which you can find in household appliances, like gas fired water heaters, grills, etc. They convert some of the heat energy into electricity which, at a bare minimum, is used to hold open a gas safety valve. Pilot light goes out, electrical generation stops, and the valve automatically closes. In some applications (water heaters) they also generate the power that the control unit uses. Pilot lights are being phased out due to climate concerns (they use more energy than you'd think) but you can still find water heaters with them. They have no connection to your household electricity. The thermocouple generates all the electricity they need.
You can find a more exotic application of the same technology in RTGs [wikipedia.org]. They aren't terribly efficient, in terms of converting thermal energy into electricity -- gas turbine handily beats them -- but they have the advantage of no moving parts and can last for decades.
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The nuclear power I'm using to write this post begs to disagree.
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The next paragraph of the article explains how this is used as an air conditioner:
The researchers then remove the heat by flowing a fluid between slabs of the electrocaloric material, while keeping the electric field on. The result is that the slab goes back to the original, ambient temperature, but has a lower polarization entropy. If the researchers then switch off the electric field, it produces the reverse effect: the polarizations become chaotic again, and entropy pours out of the atomic lattice of the ceramic, carrying heat away with it. The result is that the lattice becomes colder than the ambient temperature and it can cool fluid pumped between the slabs. The cycle then starts again.
Btw, every heat pump is both a heater and a cooler.
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Every air conditioner is also a heater and a cooler. A heat pump just lets you switch which end is which.
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Btw, every heat pump is both a heater and a cooler.
It is because of this I chuckle when I read about how people are cheering about the growing adoption of heat pumps (such as in the UK) but change into a chorus of boos when there's mention of growing adoption of air conditioners (such as in China). How often will these heat pumps be used for heating versus cooling? The reason air conditioning is hated among tree huggers is that air conditioning is considered both a symptom of global warming and a large cause of global warming, this creating a supposed pos
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Sounds like you know some people with some pretty shitty heat pumps, or they don't know how a heat pump is different from a furnace.
The last house I owned in Ohio had a heat pump, and no secondary other than the "emergency heat" electric resistive heater that only turns on if the heat pump fails. It would routinely get into single-digit (F) temperatures overnight, and sometimes stay there all day. Any my 10 year old heat pump was just fine with it, to the point where the house didn't even have natural gas
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How well do they cool?
Last year when I was looking to replace an ancient AC, install solar, etc, I looked at heat pumps but could t find solid information on cooling vs regular AC.
Re: When I hear "Air Conditioning", I think COLDER (Score:2)
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Sounds like you know some people with some pretty shitty heat pumps, or they don't know how a heat pump is different from a furnace.
Maybe I know a lot of people in the Midwest USA where the winters can bring snow.
The last house I owned in Ohio had a heat pump, and no secondary other than the "emergency heat" electric resistive heater that only turns on if the heat pump fails.
So, then you must have a pretty shitty heat pump too because a reliable heat source shouldn't need a backup like that. I've seen a lot of fossil fuel furnaces that had no electric resistance backup but every heat pump I've seen has some kind of backup, which shows how much faith people have in their relative reliability.
The big "thing" with heat pumps is that they require there to actually be some heat energy to extract from the ambient air outside when run in heating mode, so there is a reduction in efficiency when it gets *really* cold out, but that's like -20F or so with any heat pump that has been built in the last 20 years. If you are in any climate zone that remotely approaches "mild" then a heat pump is over-and-beyond the most efficient method of heating and cooling a home as long as it's properly maintained (yes, you have to clean your air handler periodically or efficiency takes a dive).
Where I live I can recall seeing low temperatures get below -20F with some regularity, and a few times getti
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So, then you must have a pretty shitty heat pump too because a reliable heat source shouldn't need a backup like that. I've seen a lot of fossil fuel furnaces that had no electric resistance backup but every heat pump I've seen has some kind of backup, which shows how much faith people have in their relative reliability.
Please read his post again until you understand it. Heat pumps are more efficient than resistive heat, but they are limited to a range of outside temperatures. When the outside temperature drops below that range, the heat pump stops producing anything and resistive heat is your only electrical option. It has nothing to do with the "reliability" of heat pumps, its just physics and economics. The goal of a heap pump is to heat inexpensively with electricity. I think my $50/mo charge just to be connected
Re: When I hear "Air Conditioning", I think COLDER (Score:2)
The biggest problem with using heat pumps for heating is improperly sized ductwork to move the air around. Other forms of heating create very hot air and that hot air can be pushed through small ducts at high velocity and still feed "warm". Heat pumps produce warm air, that if pushed around at the same velocity feels "cold". So, with heat pumps, you should have large cross-section ducts with low velocity air. But if course, that costs more, so it isn't frequently done. Especially if the heat pump is a retro
Re:When I hear "Air Conditioning", I think COLDER. (Score:5, Funny)
Get me a cheaper more efficient way to keep my house temp at a stable 72F at least....and "please take my money".
There's always the sun. It radiates free energy daily, you just have to collect it. But my understanding from reading slashdot comments is that solar energy is both woke and gay.
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The sun alone will not keep you cool. Besides he was not referring to power sources at all but instead the machinery used to condition air.
The poster clearly only read the summary or else he wouldn't see the device as only having use as a heater.
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The poster clearly only read the summary or else he wouldn't see the device as only having use as a heater.
Or understand anything about the magical device known as a "heat pump" that when an electrical signal is sent to a relay to open the "reversing valve" and cause the refrigerant to flow in the opposite direction, your cooling turns into heating. And then if you close that valve, the heating turns into cooling.
Magic!
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That's not the point.
The original post to which we all replied simply mentioned that the featured entropy-shifting ceramic device could only heat and not cool. He obviously didn't read the entire article since you can cool gasses with it as well. The article has nothing to do with sources of energy to power such devices (or any other device for that matter). Saying something like "just use solar" is nonsequitor since that says nothing about HOW you would use it.
We're really veering off-topic here by enum
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But my understanding from reading slashdot comments is that solar energy is both woke and gay.
Pretty much once you get out of California the political alignment behind energy efficient stuff completely flips. Here in FL, the suburban neighborhoods that vote overwhelmingly Democrat have little to no PV systems and gas guzzling pollute-mobiles parked in every driveway. The Republican-leaning suburban 'hoods? It's like there's practically a Tesla in every driveway and a PV system on every roof.
Anecdotally, I'm fairly certain my partner and I are the lone combo breaker in our neighborhood when it com
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Care to take a wild guess which political party is favored in our area?
Is it the one that doesn't focus on the issue, is more concerned with making the others look bad and collecting internet friends on social media?
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Is it the one that doesn't focus on the issue, is more concerned with making the others look bad and collecting internet friends on social media?
I'm sorry, but you are going to have to be more specific. Basically every political operation in the last 10 years has been "more concerned with making the others look bad and collecting internet friends on social media."
Every once in a while there's a sudden outbreak of common sense when people care more about issues than popularity contests, but the only issue that even comes close today is abortion. Everything else is demagoguery and hair-splitting, or not an issue that anyone in the intended audience
Energy efficiency flip (Score:2)
Pretty much once you get out of California the political alignment behind energy efficient stuff completely flips.
Conservation always used to be a right leaning issue. Conservation requires sacrifice and change. The rich have always been more able to handle changes or pay more for something. The rich generally have the luxury of thinking about the long term.
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But my understanding from reading slashdot comments is that solar energy is both woke and gay.
Pretty much once you get out of California the political alignment behind energy efficient stuff completely flips. Here in FL, the suburban neighborhoods that vote overwhelmingly Democrat have little to no PV systems and gas guzzling pollute-mobiles parked in every driveway. The Republican-leaning suburban 'hoods? It's like there's practically a Tesla in every driveway and a PV system on every roof.
That's because of two things:
1. Outside of California and a few other places, most Democrats aren't wealthy enough to afford those things (whereas in California, the tech industry tends to lean left, and earns relatively high salaries).
2. Outside of California, a Tesla is rare, so it's a prestige item like a Ferrari (whereas in California, I've seen as many as five of them parked in a row at Home Depot).
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I'm visiting Florida right now. Teslas are not at all rare at least where I am in the state.
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Your post cracks me up because I'm from California but visiting family in Florida right now and was wondering about the fact that I was seeing as many Teslas as I see back home while in a red state (plus I'm pretty sure the area I'm in is fairly conservative). Conservatives back home wouldn't touch one with a 10ft pole. I guess that's just the way it is here.
One of a few cultural differences I guess. Been enjoying my visit though, going for my first airboat ride tomorrow which I'm pretty excited about.
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Floridians are a practical people. Don't give a shit about "I don't buy XYZ because $politicalBullshit".
Whatever works.
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Floridians are a practical people. Don't give a shit about "I don't buy XYZ because $politicalBullshit".
Whatever works.
'gators and meth work for every situation and the best part is that buying them is an apolitical choice.
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The sun may radiate free energy, but can you collect it? If it's cloudy, no. If it's night, no.
Even if it's clear and winter, ie, -10C in the day and -20C at night, can you collect enough? How many sq meters of collectors do you need, and how many tons of thermal mass do you need to get enough heat during the eight hour day to get through the night?
PV and AC is a lot more practical in Phoenix than PV and not freezing in Minnesota. And there are too many people in MN to get by on wood heat any more.
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The sun may radiate free energy, but can you collect it? If it's cloudy, no.
False.
Yes, there is less efficiency, but the panels on my roof still generate electricity that offsets my usage on a cloudy, rainy day.
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In a refrigerator or air conditioner, heat from the warmed-up fluid would be dispersed in the environment, while the cooled fluid would serve to keep the interior or the room cold. For heating, the heat pump would cool down the external environment, extracting heat from it to be pumped into the building.
It's a standard heat pump that uses ceramics instead of compressors. Which is .. cool.
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It's a tiny heat pump for now. Useful perhaps inside a computer for chip cooling. For house-cooling they'd need to scale and something tells me this approach won't be cheap anytime soon.
Per the paper "a device that can generate a temperature difference of 20 kelvin or 4.2 watts of cooling power".
A home will need somewhere between 1 and 4kW of cooling power with big buildings even larger. This so-called science reporter probably wouldn't understand that thermocouples aren't a cost effective manner of getting
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all depends on what it costs to make the ceramic. raw materials + process.. time will tell
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The article doesn't leave out the important part: If you remove the heat, for example by transferring it to a fluid, thereby returning the material to ambient temperature, and then turn off the electric field, the orientation returns to random and this cools the material below ambient temperature. You can use this to cool a fluid, and by repeating this process, you pump heat from one medium to another.
Re: When I hear "Air Conditioning", I think COLDER (Score:3)
It sounds like the big win is that it is potentially MUCH more efficient than driving a phase change system. Much of the energy being removed by an A/C system is the energy pumped back into the system by the compressor. It's also why heat pumps running in heating mode are more efficient than regular furnaces. That compression energy is being shed into the house where you want the heat.
Re: When I hear "Air Conditioning", I think COLDER (Score:5, Insightful)
That remains to be seen. From TFA:
Defay says that although the technology is not yet ready to be commercialized, with further refinements, the efficiency of his team’s electrocaloric heat pump could be competitive with that of existing heat pumps.
More accurately, much of the energy of the work of the compressor is wasted when the pressure energy is not recovered at the expansion device. The heat from the inefficiencies of the compressor does have to get removed by the condenser, but that's just calls for a little more condenser coil and a slightly bigger condenser fan.
The rise in temperature from the compression of the refrigerant is what is used to heat the indoor air, but you're still losing the pressure energy at the expansion device at the outdoor coil. It is only the inefficiencies of the compressor and the indoor fan that contribute extra to the heat output of the system. Even disregarding that extra heat the heat pump is much more efficient than an electric resistance heater (or gas heater, depending on the efficiencies in making electricity in the first place)
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From TFA:
"But the laws of thermodynamics say that the total entropy of a system can never decline, so if it falls somewhere it must increase somewhere else. “The only possibility for the material to get rid of this extra mess is to pour it into the lattice” of its crystal structure, he says. That extra disorder means that the atoms themselves start vibrating faster, resulting in a rise in temperature.
The researchers then remove the heat by flowing a fluid between slabs of the electrocaloric mate
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This technology can create a cooling or heating effect just like a heat pump using current technology. It cycles the electrocaloric material on and off, and between cycles can use a nontoxic coolant fluid such as plain old water or glycol solution to transfer heat away from the ceramic material to an outdoor unit where the heat is discharged to the environment. It's essentially quite similar to an air conditioner, but replaces the compressor and refrigerant gas with a fancy ceramic material and a water pu
Re:When I hear "Air Conditioning", I think COLDER. (Score:5, Interesting)
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On top of eliminating Freon it sounds solid state? Well you still need a pump to move the heat where it is needed but no compressor. Sounds potentially very reliable.
Well no. The summary leaves out the bit about the effect being temporary. The material will eventually reach ambient temperature. Then when the electric field is stopped, the material heats up.
So this isn't a continuous process. Flow across the material will have to be redirected or the material will have to be moved so the heat can be rejected in a suitable location.
Although the material itself is steady state, the final product will require a lot of moving parts.
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If it ever becomes viable, it could be something like a heat wheel. [thermotech-usa.com]
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If it ever becomes viable, it could be something like a heat wheel. [thermotech-usa.com]
Yeah, I was thinking along those lines. A thermal wheel [wikipedia.org] with brushes like a DC motor to control the charge should continuously push heat in one direction.
I suppose you could think if this device like a thermal magnet, and apply it the same way magnets are applied.
Air conditioning is not "COLDER" (Score:2)
The reason HVAC system use the term "Air conditioning" isn't because that means "colder" or "hotter". It's because the air has to be "conditioned" before it can be cooled or heated. Bear with me and I promise to leave out the hard math wah wah.
Cooling is a human concept. So is heating. In the science world we move excited molecules. If we exchange really excited molecules (fast-moving hot ones) with slower moving less-interested molecules (slow-moving cold ones) then we lower the ambient temperature ak
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To first "condition" the air, we must remove moisture. So the first thing an HVAC system does prior to cooling the air is condense the moisture out of the air. That's what that drippy-drip pipe leaks out of the condensor when you fire up the HVAC is doing. Once the air is sufficiently dry then the exchange of molecule energy begins and cooling occurs.
It is true that an air conditioner dehumidifies and cools the air but as you describe it this looks like a two step process. I'd describe it more as the air conditioner dries the air as it is cooled in a single continuous process. Cooler air cannot retain humidity as well as warmer air so by cooling the air some of the humidity condenses out, and this condensed water is collected to be drained away so it isn't reintroduced into the air later.
One reason for calling these devices an "air conditioner" versus
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I know this is Slashdot, and nobody actually reads the articles. But in this case, to get the cooling part, you do have to read the article, which does explain how the system would head *and cool* a house. This is similar to other kinds of heat pumps, which can also both heat and cool.
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I know this is Slashdot and all but people need to stop looking at science articles from science reporters and go to the source and read the paper. Even just the synopsis would be sufficient to understand that this is cool science but nowhere near applicable for home cooling.
Whenever someone makes a bold statement that they will revolutionize the world, get yourself a bucket of salt.
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I know this is Slashdot, but people who want to complain that ${TECHNOLOGY_X} isn't available at Wal-mart might be happier browsing Amazon instead of Slashdot.
This is interesting new technology, i.e. what Slashdot is supposed to be about.
And the story title said "could."
Re:When I hear "Air Conditioning", I think COLDER. (Score:4, Informative)
Get me a cheaper more efficient way to keep my house temp at a stable 72F at least....and "please take my money".
Better insulation is always going to provide more bang for your buck than any gains you can hope to get from more efficient HVAC equipment, unless you're running some relic of an air conditioner that belongs in a museum.
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Better insulation is always going to provide more bang for your buck than any gains you can hope to get from more efficient HVAC equipment, unless you're running some relic of an air conditioner that belongs in a museum.
If you ever replace the siding on your house, make sure to add some foam board insulation underneath. It can save a ton on energy bills!
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I'd vote air gaps, at least in older houses. Anything built in the last 20 or so years has a tightly sealed envelope. And if you have air gaps, insulation has limited benefits. Drafts > insulation.
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Anything built in the last 20 or so years has a tightly sealed envelope.
Which worked out real well during COVID.....
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Feel free to use the volume of the house divided by the air leakage rate as the key figure of merit.
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This is why a lot of A/Cs have an air purification system using UV light and HEPA-grade filters. Of course, extra stuff means extra stuff that breaks.
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I used to think that, but I kinda like the ventilation, though my house isn't leaky compared to my previous house. True, a heat-recovery exhaust/intake ventilator would be better, but not easy to retrofit into my house. Also, windows are big sources of heat gains in the summer and heat losses in the winter. If replacements weren't so damn expensive, they would be a good target for improving efficiency.
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Actually, air conditioning is called that because the original application was controlling humidity.
Carrier (yes, that Carrier0 worked at a print shop, and discovered on humid days the printing machines would jam up more often.
We knew the basics of moving heat around, and by doing that, Carrier discovered he could "condition" the air by controlling the humidity. Hence, why it's called "air conditioning" and not just "air refrigeration" or "air cooler". The refrigeration cycle was well, know, as as its abili
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Yes. It would be. As old units die and get replaced anyway, you use these.
When new construction requires a unit, you use these.
After 10-20 years you'll be near 100% replacement.
What made you think everything had to be replaced at once?
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Run it once, it heats up, run it again, it cools down.
In short it's replacing the coolant in a regular AC unit so you don't have to pump around the compressed hot liquid/gas, let it decompress which will cool it, then recompress it, all the while cycling it back and forth so it absorbs heat from inside, and releases heat outside.
Now they can have those ceramic thingies switching phases to absorb
Switch to celsius (Score:2)
>> Get me a cheaper more efficient way to keep my house temp at a stable 72F at least.. :)
Switch to celsius
A few questions (Score:5, Interesting)
How much electricity does it take for this to work compared to a compressor?
How fast does the cooling take place?
How hot can this get if you're using it as a heat system?
As above, how long does it take for heating to take place?
What is the expected lifetime of the components compared to a compressor?
Is this replacable like a compressor?
Can it work in cars/trucks?
Scalability?
Not nitpicking, just asking legitimate questions.
Link to more info (Score:3)
[Lots of questions, deleted]
Here's a link [science.org] to the journal article.
Is it too much to ask Slashdot editors to include relevant links to papers, so that we can push through the inevitable tech reporter disinformation? It took only 5 seconds to find this one.
It would make Slashdot so much more better, but then only if the editors cared about that.
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Compared to the Carnot limit would be the obvious interpretation.
Just like one could call even state-of-the-art solar cells inefficient. It's simply a fact.
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Uh, yes, something that's more efficient DOES give it promise.
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Then, can this be constructed and sold to the consumer for low cost? Because if it has no ROI there's no reason to rip out a perfectly good AC compressor for one.
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They're not stupid. This site just doesn't make enough money to bother so we get the short stick.
Love it, but still in the concept stage (Score:2)
As all of us software engineers know, ideas are the easy part, turning them into something concrete, at a price that fits within a company's (or person's) budget, is a whole other matter.
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For physical engineering, that is a bit different. (For software too, as soon as you leave simple things behind...). The idea is the needed starting point and it is _not_ easy to find.
What's the delta temperature? (Score:2)
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Peltier systems are completely different. Even so, they can provide a temperature differential of up to 70C in a single stage, and you can stack them.
Your cooler just has one that's too small.
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>> your stack air conditioner would be like running an arc welder. :)
Yeah, but how do you cool the welder, then
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Peltier systems work similarly,
Nope. Different system entirely. Moving charge carriers carring differenct amounts of heat between hot and cold ends, vs. locked-in-place atoms becoming more or less spin-aligned, and hotter or cooler, as a field is applied and revoved, with the heat moved to the hot end or from the cold end by a pumped fluid.
You can add a little heat, or pull out a little heat, but it's not gonna make ice in the desert.
Or you can stack them in series in a shrinking pyramid and reach cryogen
Useless article, useless idea (Score:2)
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It does say, admittedly vaguely, that it 'could be competitive' with conventional heat pumps.
That would seem to indicate that 3.8 is a theoretically reasonable target.
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Since they're claiming a delta-T of only 20K at (presumably) room temp of 300K, the heat engine efficiency would be about 7% so as an AC the inverse of that implies a theoretical COP of 15 and 2/3 of that would be a COP of 10?
A relevant comparison point is magnetocaloric fridges. Only very recently have they reached the point of having useful efficiencies and the ability to operate at room temperatures. The claimed efficiency for this electrocaloric devic
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Making it true solid state will probably not be as efficient. Not impossible but you would need to make it with at least two stages in series, pushing the heat to ambient in an undulating fashion.
With just the single stage you need either a mechanical pump pushing fluid around, or put the ceramic on something like a wheel and rotating it similar to a desiccant wheel.
Still use fluids (Score:2)
If I'm following the description correctly, it causes heat to move across the special substance, which can make it cold on one side and hot on the other. At first thought, this sounds like power consumption will be proportional to the distance the heat is moved, which is not going to work well moving heat between inside and outside of a building. But if you use this to heat or cool a fluid outside and then pump it inside, it will work great. This gets rid of the compressor, but you still have a pump to m
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If I'm following the description correctly, it causes heat to move across the special substance, which can make it cold on one side and hot on the other.
Nepe. It's a chunk of dielectric in a capacitor that gets hotter as the capacitor is charged and colder as it's discharged. You have to bathe it in a fluid and pump the fluid past it and to the cold or hot ends of the system at the appropriate times in the charge-discharge cycle (or do some other auxiliary heat-moving thing).
if a new kind of heat pump lives up to its promise (Score:2)
If the new kind of zero coupon inflation protection bonds live up to its promise, all retirees will be rolling in money and be donating millions of dollars to get rid of mosquitoes in equatorial New Guinea....
See? Anything is possible if you add an if at the beginning ...
Cost and efficiency? (Score:2)
Idea not that new, the scaling is the problem (Score:2)
Become redundant? (Score:2)
That only makes sense if the electrocaloric system is capable of doing the environmental damage all on its own, without the use of the referenced gasses.
Who writes this stuff?
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Getting rid of the coolant is a really, really big win.
Not really. There are plenty of refrigerants which are completely harmless to the environment. As often seems to be the case though, the real issue is economics. It you're going to build a better mousetrap in the HVAC realm, it has to be cheaper to install, maintain and operate than existing solutions.
For example, solid state thermoelectric cooling has been a thing for quite awhile. You can even see the technology commercialized as novelty soda can coolers sold at Walmart. Why aren't they more widely u
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...and in addition to economics, sometimes certain types of perceived safety. For example: ammonia, propane and butane are excellent, cheap and widely available refrigerants. They aren't allowed in residential or most commercial units because there is a theoretical risk of explosion if the gas leaks into the building.
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Actually, flammable refrigerants have been allowed for awhile now in residential use, depending on the application. Small refrigerators can be charged with R-600a (isobutane) which is basically highly purified cigarette lighter fuel, and window air conditioners can be charged with R-32 (difluoromethane) which is classified as an A2L (slightly flammable) refrigerant. In vehicles, we now have R-1234YF (2,3,3,3-Tetrafluoropropene), which is considered mildly flammable.
So no, while realistically flammability
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They (ASHRAE, mainly) have had 3 classifications of flammability for refrigerants, 1 - not flammable, 2 - low flammability, and 3 - high flammability. But they recently split the low flammability classification in two, creating a 2L classification for low flammability refrigerants with low flame propagation velocities. They seem to have done that for the purpose of expanding the use of some
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RV absorption refrigerators, the ones that use propane to chill your beer, have hydrogen and ammonia as part of the cooling cycle. RV fridges used to be a common cause of fires, but the "fix" that RV makers are doing, is switching to compressor fridges and using solar, or a propane fuel cell. As an added bonus, the fridge doesn't have to be level (absorption fridges need to be within 3-6 degrees of plumb, otherwise the propane flame will cause calcium citrate, an anti-corrosive agent, to precipitate and c
Propane aircons are common in some countries (Score:2)
R290 (Propane) refrigerant air-cons and heatpumps are legal in the EU subject to certain air volume restrictions (ratio of total system gas to room air volume). In practise this limits its use to mini-splits, and monoblocs (the later all refrigerant is kept outdoors). Same goes for India I think.
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I don't know about residential applications or what the laws in different jurisdictions are but there is a guy on YouTube who posts videos about fixing refrigeration equipment and he works on commercial restaurant equipment in California that uses R290 propane as a refrigerant so its legal to use there at least.
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...and in addition to economics, sometimes certain types of perceived safety. For example: ammonia, propane and butane are excellent, cheap and widely available refrigerants. They aren't allowed in residential or most commercial units because there is a theoretical risk of explosion if the gas leaks into the building.
Untrue in Europe. Yes, you get some dire warnings with them, but both my fridge and my air-conditioner (mobile, for those few days it just gets too hot) are on Propane. Unless you do something stupid like puncturing the copper tubing, these are perfectly safe. I also keep wondering why lighter gas refueling cartridges (much more volume and likely much more dangerous) come with regular warnings only.
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64% carnot efficiency is not at all inefficient (let alone "hopelessly").
And even if that weren't the case, it'd still be heaps better than peltier coolers, but with the same form factor.
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Hahaha, yes. Peltier is hopelessly inefficient, Wikipedia says 10-15% compared to 40-60% for compressor based. They are for special uses only. In practice, 40-60% is pretty good. Anybody calling that "hopelessly" just has no clue.
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is it my imagination or is a breakthrough in materials at the root of every solution to a host of problems.
It is. Material sciences are in no way at the end of what they can do. For coolant, this is not urgently needed though. For example, Propane (R290) really works fine in most applications and the minuscule amounts used in heat pumps does really not matter compared to other sources and effects. If it has a greenhouse effect at all, I was unable to find data.
Re: Peltier cooler? (Score:2)
No. The peltier cooler runs continuously on DC. This thing concentrates heat while turned on, then it is turned off and the heat is removed, repeat as necessary.
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The GPs phrasing is better. The "disorder" in the atomic polarized atoms is heat. Applying an electric field moves this energy to the crystal lattice (i.e. concentrates it there) where it can be removed by a coolant. That's why the process is efficiently reversible and stuffing heat back into burned fuel or a wire heating element isn't.
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Technically, heat is the energy transferred by a difference in temperature, and if it's not moving from one body to another, it's not heat. So the internal kinetic energy of the vibrating atoms is not heat, even though the word "heat" is often used for it.
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Heat is the energy transferred between systems by a difference in temperature. The orientation of the polar molecules and the vibrations of their lattice are easily regarded as different systems.
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Thermoelectric != electrocaloric. Very different principles.
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It uses a different [techxplore.com] cooling process, and because the hot end and the cool end are separated, which gives it a better COP (coefficient of performance) just because of that, as well as reaching the limits of a Carnot cycle, it is a lot more efficient than a Peltier cooler.
There are even more efficient systems out there. This [youtu.be] comes to mind, although other than the YouTube post, I've not seen much come of it. This system can use solar, not for PV and electricity, but for heat which can push the coolant along,