French startup unveils new residential thermo-acoustic heat pump | Hacker News Reader

French startup unveils new residential thermo-acoustic heat pump

pv-magazine.com

540 pointsperpil219 comments

Super cool to see someone trying to commercialize this technology. Fun fact is that the JWST cryocooler operates on a similar principle (although the implementation is quite different).

Relatedly, I found this fantastic video on to how to use the thermoacoustic effect for heating and cooling a few months back: https://www.youtube.com/watch?v=kkBBkQ8jFRY

I expect to lose karma for saying this, but it’s not just super cool but also super hot.

You just couldn’t help it

no problem, just chill out

Thermoacoustics, so hot right now.

Hear hear, so hot it's so cool !

The most innovative heat pump we’ve seen in years.

Hyperspace Pirate on YouTube is working a DIY Pulse Tube Cooler that also uses thermoacoustic principals. His videos go into quite a lot of detail about the various parts and how they need tuning for everything to work.

https://www.youtube.com/watch?v=WOmjJFk8rl0

>in a closed-pressure vessel filled with helium at a pressure of 30 bars...

>It has a 30-year lifetime, with an easy installation process

Normally, any kind of pressure vessel (steam, compressed gas cylinders, etc.) is subject to routine inspection and hydro-testing for re-certification.

What happens if/when it needs to be serviced? Do I need to draw down a crazy level of vacuum before charging it helium (or whatever working fluid)?

>Traditional fixed-output units cycle between on and off multiple times a day, switching between zero and maximum capacity to achieve the right temperature balance. But the new heat pump modulates its output to continuously provide the desired temperature.

New heat pumps / air conditioners already do this with variable speed compressors and fans.

There really isn’t such a thing as a “crazy amount of vacuum”. The most vacuum you can have is 1 bar. From a structural standpoint there’s no difference between a very bog standard vacuum, like say the 2psia or so a vacuum cleaner produces and a 10^-10 physics lab vacuum that takes hours of pumping.

From the stress on the system perspective you are right, hard vacuum is not significantly more stressful on the container than low vacuum. But I think the parent was talking about the cost of maintenance. If the pressure vessel needs recertification over it’s lifetime that will be expensive. If refilling the container requires high purity (and therefore more work removing the air and other contaminants before filling) the process will be even more expensive.

This has been a pet peeve of mine for a long time, am I correct to assume that deep vacuum is only hard to maintain because very very small impurities in seals etc will cause a relatively large amount of off-gassing?

Not only that, but at those levels of vacuum you’re getting all kinds of outgassing from the object in the chamber.

Helium and hydrogen can also fairly rapidly diffuse through materials or grain boundaries and contaminate the vacuum.

Should not be a problem here as the vacuum (if it's needed at all) would only be temporary to "make room" for high pressure helium. That would only be required if the helium had to be of particularly high purity and gp wasn't at all implying that this is the case, only that it could be a challenge if it was. From my uninformed perspective, it's just as likely that impurities would condense at the bottom and rest there happily ever after as they would be thrown into an permanent phase change cycle that rims efficiency even in trace amounts. The best case scenario I'd like to read is "actually we don't really need helium but it gives a slight performance edge over other gases and we decided to launch with the setup that gives us the best numbers". No idea if that's close to or very far from reality.

Yah, I don't think its a problem here, just a general response to the comment about acheiving and maintaining ultra high vacuum.

It also just becomes difficult to motivate the gas towards the intake of the pump.

IIRC turbomolecular pumps, which are used for deep vacuum applications, have a large intake area and work by basically spinning a huge array of blades at very high speed to bat the individual gas particles out of the working volume into progressively higher pressure areas, ultimately pumped out by a conventional pump.

And then are ion pumps. They have no moving parts at all.

An ion pump (also referred to as a sputter ion pump) is a type of vacuum pump which operates by sputtering a metal getter. Under ideal conditions, ion pumps are capable of reaching pressures as low as 10−11 mbar.[1] An ion pump first ionizes gas within the vessel it is attached to and employs a strong electrical potential, typically 3–7 kV, which accelerates the ions into a solid electrode. Small bits of the electrode are sputtered into the chamber. Gasses are trapped by a combination of chemical reactions with the surface of the highly-reactive sputtered material, and being physically trapped underneath that material.

https://en.m.wikipedia.org/wiki/Ion_pump_(physics)

Will we ever get those structural vacuum balloons that enable more floaty things, like the mites in Neal Stephenson’s “Diamond Age?” Or like the giant floating geodesic ball proposed by buckminster fuller?

I was reading about early Royal Society proposals for flying machines that were based on vacuums in copper balloons. Can any material at any size support a vacuum that can displace the weight of the material? (ie, and thus support lighter than air flight via vacuum)

No, even carbon nanotubes aren’t strong enough.

Hydrogen is already nearly a vacuum from a lift prospective (it’s only about 5% as dense as air at the same pressure).

Those "structural vacuum balloons" are a nice idea but they will have to be made to degrade in sunlight - or else chunks of them will end up cluttering the upper atmosphere, sorta like low-flying space junk.

You’ll also get gaseous diffusion through most materials from the atmosphere, offgassing as you note, plastic and other materials decomposing, etc.

Nature really abhors a vacuum.

It’s not difficult for a pressure vessel to withstand a hard vacuum, it’s difficult to achieve a very low vacuum. Lots of things offgas, lots of things are gas permeable enough to ruin your low vacuum, just getting equipment that can achieve a certain amount of vacuum is hard and expensive.

The question is: does maintaining this require a very high vacuum to replace/maintain the working fluid. Its one of those scaling problems where you have to spend ten times as much to get to the next ten times less gas in a vessel (or thereabouts) and an absolute complete vacuum is more or less impossible.

That's true, but according to the article the pressure vessel holds He at 30 bars.

Ok? The way you test that is by pressure testing it at 35 or 40 bar, not -1

I should have been more clear. I'm empathizing with the service technician. By "crazy amount of vacuum", I'm referring to amount of time required for pumping / dehydrating the system.

Dehydrating maybe… pretty easy to depressurize since you can safely vent nitrogen to atmosphere.

The default seems to be 4 years visual inspection and 10 years periodic pressure-testing in France (I suspect it's general air compressor). https://www.legifrance.gouv.fr/jorf/id/JORFTEXT000036128632 I don't have time to read all of that. Skiming, I see the manufacturers have a wide latitude to create their custom maintenance schedule. Interesting detail, the thresholds for inspections are given in uncompressed volume (pression*compressed volume), I guess it's directly proportional to stored energy.

I would expect a more relaxed inspection schedule in this instance because there is no significant cyclical loading of the pressure vessel, and since there is no water ingress, internal corrosion should be fine. Vibrations taken as cyclical loading can be swallowed in the bathtub curve, since you get 30000 cycles in the first second, and very little variation of stress at each cycle.

edit:

- appendix 1 if the vessel has non-corosive gas and not been de-pressurized, internal inspection is not required. Internal visual inspection only if re-pressurizing it and last visual inspection is more than 4 years old.

- you seem to be able to replace the water pressure proofing test by an untrasound test under pressure with the nominal gas, but the document describing the procedure ("Guide des bonnes pratiques pour le contrôle par émission acoustique des équipements sous pression") seems to be behind a paywall, so I don't know if it's done at nominal pressure or if you need to open the vessel

Different pressure vessel materials have different characteristics. Just changing the alloy can make a major difference. Since there are thousands of alloys, and new ones are developed once in a while, it would be inappropriate for the law the create one inspection schedule.

Plain steel corrodes, so an inspection that it isn't corroded should be done once in a while. Plain aluminum doesn't corrode, so a visual inspection won't find anything, but the fatigue characteristics means that you need to count cycles and stop using it after some number of cycles. There are many other elements that can be used for pressure vessels (though iron and aluminum are most likely), and you can alloy them in different ways.

Of course there is more than visual inspection, sometimes ultrasound and x-ray inspections are done, each will show different things, and each requires different training to do.

In Italy, for fire extinguishers, there is a "new" norm (2013) UNI 9994-1:2013 that essentially prescribes for them an overall lifetime (besides the need for periodical inspection/maintenance/recharging/re-certification) of 18 years, i.e. anything manufactured in a given year, 18 years later must be replaced with a new unit.

For other pressurized tanks, I believe a line is drawn at 12 kg/cm2 (it depends also on size, those smaller than 25 lt are excluded), those up to that pressure have periodical visual and pressure tests (every 2, 3 or 4 years depending on a number of factors), those above that have additionally those (ultrasound) checks for the integrity every 10 years, but the norms are complex, no idea which specific ones may apply to this thing here.

30 bar is not a lot. A SodaStream CO2 cylinder has twice that at room temperature [1]. The pressure inside your air conditioner is probably not much lower either. I would be very surprised if a 30 bar vessel for an inert gas required routine inspection.

[1] https://support.sodastream.com/hc/en-ca/articles/44038019714...

If it needs to be serviced, you either vent the helium out (unlikely to happen due to cost of helium thesed days and the volume that will be needed if this becomes a common appliance in households) or move it to another container so you can repurify it at a plant if you are worried about contamination (unsure how much purity those devices need).

To refill after maintenance you may also just purge with helium (or another cheaper gas that doesn't impede behavior of the device) then pressurize with helium .

So mostly a non issue. And there is really little safety issues with this kind of constant pressure containers containing non toxic gases just a routine inspection should be enough as they can be made of high quality materials and shielded.

I do wonder why we have odd situations like a fridge inside a house that's using energy to keep stuff cool because the air in the house is being heated to keep people warm because it's cold outside.......

And of course that we're leaking heat in various ways such as the output from sinks, showers or baths and in the form of stale air but a heatpump cannot scavenge from these.

It would seem logical to have some sort of "temperature management system" which could move heat around from the various points to make use of whatever natural sources and sinks were available at that time of year.

In the same spirit- a home has dozens of power bricks converting AC to low voltage DC. You would think a central high quality unit could do that… though an obvious drawback is additional wires to snake around…

I would love for this. Low voltage DC has fewer, simpler requirements for building code and can be easily run through walls. Additionally, it would help a lot of the heat dissipation issues with LED fixtures. The only problem is the eventual voltage drop from long runs...

could almost treat it like an in-house network with a few AC/DC converter "hubs" scattered around where you need them, if the distances are too long, or the device load too heavy.

I have been toying with the idea of converting my old telephone wiring to a 24/48VDC system for charging DC devices. A switch mode DC-DC converter is extremely efficient, and would be a net improvement over multiple disparate USB AC adapters.

Unfortunately, it's just not that useful for my home. We don't have enough devices that charge concurrently to justify it

It's more efficient to use many 90ish% efficient switch modes supplies for AC to low voltage DC than to run 12/5v all over the place because the resistance of those wires makes any sort of distance inefficient as all hell.

Also you'd end up needing hella fat wires; if you want to run 12v everywhere but say your cumulative prospective 12v consumption is like 2kW then you'd need wires for the trunk lines that are like 20mm diameter! (like 160A)

A heatpump probably won't scavenge energy from the exhausted air, but a HRV could

This is why there's an advantage to putting the fridge in the garage. If its 40* in the garage, the compressor won't turn on.

I was just quoted this week for a CO2 heat pump set up that promises 62 deg Celsius water output with COPs that are at a range similar to that of regular heat pumps. The details on this company are scarce, so I'm treading cautious.

Claims COP A7/W35 (I can't tell what A7/W35 means) of 4.8!

https://www.durocan.com/specificaties/

https://www.durocan.com/co2-heat-pump/

Curious if folks who know about heat pumps here have any opinions on this.

EDIT: It appears to be a Dutch company (I live in NL) that has licensed the CO2 heat pump tech from an American company - https://www.smallplanetsupply.com/sanc02

A7/W35 means at 7°C air input temperature and 35°C water output temperature.

It's only 2.8 at -8C though. The best heat pump on https://ashp.neep.org/ [1] has a COP at Max Capacity @5F (-15C) of 3.7

[1] https://ashp.neep.org/#!/product/56885/7/25000///0

This is a popular recommendation from green-building advisors in USA. I ended up rejecting it and buying a more standard hybrid (heat-pump) hot water heater from Rheem because of a) cost, b) plumber familiarity, c) payback time

We installed a Sanco2 on our house a few months ago. It's been performing as advertised so far. Impressive little unit.

It was 7X the cost of just replacing the gas-fired heater. However, we turned the space the previous heater occupied into a much-needed pantry, significantly reduced pipe runs, and removed a source of combustion from inside the building envelope, which made up for the cost difference. Happy to answer questions.

Glad to hear that. May I ask where you are? I live in the Netherlands and am looking at it to provide hot water for underfloor heating and tap water. Curious what your setup looks like? and how it performs in winter when one would actually use the heating..

Switched to email. Anyone else is welcome to email as well.

That's very interesting to see!

The first time I read about acoustic heat pumps was when the Dutch governments' research arm spun off their start-up: Blue Heart: https://www.blueheartenergy.com/

I had no idea multiple companies were pursuing this. That's great! If we can replace every gas boiler with a acoustic heat pump that can produce 70 degree water that will enormously speed up the electrification of domestic heating in Europe.

BlueHeart Energy ( https://www.blueheartenergy.com/ ) from Netherlands also has developed a new heat pump that uses thermo acoustics. The technique consists in creating sound waves in a closed circuit to generate heat and cold.

Why do I picture me walking down the street, and all around me heat punps are screaming?

A cartoon of them actually screaming, is in ny head.

My neighbour has a large, fully electric house, no more gas, in a Dutch climate (winter ± 0-5 degC). I do feel that that property (which was very expensive) makes quite some noise indeed. His heatpumps, but also his solar converters in the Garden (where he has a small field of solar panels). And then he has some automated watering system that pumps from the canal into his garden... It's not loud, but it also not quiet. I don't like it.

probably if you are trying to understand how this works it would be useful to read https://en.wikipedia.org/wiki/Thermoacoustic_heat_engine

Thanks. I was trying to square the very first sentence of the article "Equium has developed a new thermo-acoustic heat pump core that reportedly produces 3 kW to 4 kW of heat for every kilowatt of power it consumes." for not violating the first rule of thermodynamics.

Yes, this regularly comes up with any heat pump discussion. Strictly speaking, it is not producing heat, it is moving heat from outside to inside (or vice versa for an air conditioner, or for that matter, a refrigerator).

⅔ to ¾ of it anyway

This and the posted article mention a speaker or driver. No mention of how they deal with aging or fatique effects in e.g. a flexible ring connecting to the frame and holding the cone. Have done applications where a special "high cycles" acoustic driver had to be sourced.

i hadn't thought about that; it seems especially important given that they're talking about kilowatt power levels and macroscopic wavelengths, so a nice piezo probably won't cut it

how did you source the high cycles driver, what was it made of, and how much did it cost

I just found this[1] which mentions rubber vs. foam surrounds (suspensions), and butyl rubber with apparent good life. (That might have been the simple difference; the normal-looking speaker was already sourced; I came in to do embedded/DSP.) At kilowatt/constant power levels I'd imagine going as far as oil/magnetic suspension for high life; even o-rings under high cycles can fall apart.

I'm pondering how one would do accelerated reliability/life testing for the acoustic heat pump application. Maybe they have good-enough FEA/multiphysics on a suspension and cone, and strain/life curves they are prepared to trust. With a slope on log-log strain vs life they might project how much to overpower/overstrain for an e.g. 1000hr accelerated test.

[1] https://www.avforums.com/threads/speaker-life-expectancy.164...

thank you very much

The founder of the startup made a speech to TEDx [1] (in French). He is the son of one of the precursor researcher on thermo-acoustic. The speech gives some possible applications of this new technology.

[1] https://www.youtube.com/watch?v=-soze8e2Quo

I wonder if this tech has the efficiency of a turbine and if it could be used to extract power from nuclear fission.

It's awkward to compare this to a turbine. In a sense they're opposites, one uses mechanical energy to create thermal gradients, the other turns thermal gradients into mechanical energy. However while a normal pump is sort of an engine run backwards, the heating efficiency of a heat pump is because it's moving heat, not because it's efficient at turning motion into heat. Finding a way to run this device "backwards" would not make for a good generator.

>turns thermal gradients into mechanical energy

This tech does this too, you can see here: https://youtu.be/wg96lDw7sNw

Wow, interesting. I can't watch now, but thanks for the link.

the cringe level of that video is over 9000. it looks like a startup founder imitating a standup comedian imitating a tedx speaker (maybe he does not have an audience because of covid, that's why it feels awkward)

> produces 3 kW to 4 kW of heat for every kilowatt of power it consumes

So, not too different from typical heat pumps. Ground-source heat pumps are especially effective.

Although it feels like a nice value for a first model in the market.

I find interesting that's very silent, and has a nice range of work temperatures. And the "no refrigerants" part too (although it needs some helium, though).

No info about the price.

funny, I read the same thing, and had the optimistic view that maybe this is not a scam, they are not claiming crazy numbers. I suppose that since scientific machines use this apparatus, their design space has been explored in great details.

I remember reading about thermoacoustic devices 20 years ago, probably from the following article: https://www.popsci.com/scitech/article/2004-05/chilling-soun...

I think the reason that they haven't seen adoption isn't that they're a scam, but rather because they're more expensive than traditional approaches (not quite sure why, or by what margins). However, since our attempts to replace freon with ever-more-exotic refrigerants seems to inevitably fall face-first into environmental disaster, it's possible that a non-greenhouse-gas approach could be regulated/subsidized into existence, if it's not too much more expensive.

> hot water at temperatures of up to 80 ℃

> level of noise is reportedly lower than 30 dB

If it can provide water hot enough for residential use, and be silent, then it's a huge improvement over existing typical heat pumps. It would no longer need an additional boiler to get the water temperature up.

Isn't this working at a significantly higher ouput temperature? Typical heat pumps are nowhere near COP 4.0 when outputting 80C (about 60C delta)

They don't, as far as I can tell, claim that. There is a claim of SCOP of 3-4, and a claim that they can output 80C, but there isn't a claim they can output 80C at a SCOP of 3-4.

Good point. It had slipped past me.

The latter definitely is more plausible

You can't install a ground-source heat pump in the middle of the city.

In Scandinavia this is routinely done via boring very deep wells, like 300m, https://hvac.okstate.edu/sites/default/files/pubs/papers/201...

This may not be suitable for skyscrapers, but it works for 4-5 store apartment blocks.

Under a parking lot?

Could be in a building's basement too.

This sounds a bit puzzling to me, so probably I'm missing something. 1 kW of electricity (eg. 200V at ~5A) turns into 3 kW of heat. It would mean we are creating "work" from nothing, which sounds impossible to me. How does that work in fact?

Don't think of it as creating 3kW of heat, think of it as using the electricity to transfer that much heat.

COP vs. efficiency. In the case of a heat pump, it takes 1 kW to “move” 3 kW of heat, rather than turning 1 kW into 3 kW.

Its pumping heat from its the "outside", as you know heat flows from hot to cold, and the gas in this case (uncompressed helium), is colder than the outside, absorbing heat from the outside.

For typical heatpumps efficiency is a factor of temperature difference. Ground-source are efficient (COP 5) because you go from 5 degrees Celsius to perhaps 35 degree Celsius (underfloor heating or low temperature convection radiators)

This invention claims COP 4 for heating water to 80 degrees, that is a huge step up.

For instance it changes the game to replace oil and gas heated radiators, as you can only replace the heat source, not radiators that only work well with 80 deg C water (where COP is very bad for conventional heat pumps)

I wonder what the efficiency is at higher temperature differences.

For example, I would like a water-sourced aircon which cooled a radiant or chiller circulating system on the cold side, while heating incoming water for hot water on the hot side (plus an 'overflow' cooling ground loop if necessary). Maybe this isn't beyond the ability of current systems, but I think having a fairly large gap of 60C hot/5-15C cold is inefficient currently, and maybe a reason you don't see this obvious setup too often.

A standard heat pump water heater does that but will only provide a couple degrees of cooling to meet standard domestic hot water needs. You can also get pool heater heads for heat pumps/ac units though last time I looked not all were available in the us.

Yes that's a great idea. When I said 'overflow ground loop', I obviously I meant 'dump any excess heat into your swimming pool'. In fact this surely makes sense for existing aircon, just for better efficiency.

Would this work to replace the compressor and refrigerant for refrigeration? Fridges that last need less repair and have nothing to leak when they do need repair would be pretty neat.

There is helium inside. Very leaky. But, I think, you mean that helium is non-flammable and do not do any environmental damage.

The article doesn't state why they are using helium. Could the same be accomplished using some other cheaper, less leaky gas like N2?

I'll speculate that since it's compression and decompression (as opposed to phase change) that's being exploited, you need a small gas whose behavior is as close to the ideal gas law as possible. Smaller gasses are also more volatile and leaky though, so there is probably some tradeoff.

> The article doesn't state why they are using helium

FTA: Because helium remains a gas until -200 C, we can achieve higher temperatures inside our heat pump core

N₂ boils at −195.8 °C, but that will be higher at 30 bar.

A quick look at a phase diagram I found online suggests the boiling point would be somewhere close to -160C at 30bar.

Hard to see how that would be a problem in this application.

I would suspect that N2, being diatomic, has vibrational and rotational modes which would cause a bit of inefficiency in the cycle.

Would be interesting to see how much.

A helium leak is not as bad as a refrigerant. Also given it’s solid tune with no moving parts, I would think the leakage of helium would be minimized.

*tube

I’m wondering how or if helium supply issues might make impact scalability of this. Yet another in a long list of reasons we should ban selling the stuff to the public.

AFAIK Natural gas extraction produces a whole lot of helium. We just have to bother to capture it.

(Please correct me if I’m wrong. I read it on slashdot decades ago)

You're correct.

There's no shortage of helium, at least for several hundred years. There just aren't many gas wells capturing it because it didn't make any economic sense to do that until recently.

That is true, but OTOH if we're going to address climate change we can't keep on extracting natural gas like there's no tomorrow. So helium could become a pretty expensive thing.

It's right, and it's not expensive enough to have large scale recycling and conservation measures (some scientific labs have recycing systems already, but they are not the ones wasting the most). It's one of those cases where there is a shortage "at that price".

What exactly would you prefer helium to be used for other than quiet, efficient heat pumps?

Banning the sale of helium is foolish. The market is already responding to less supply, as it always does. We don't need people running around stopping innovation because they don't understand how price signals work.

Kinda fuzzy on how this works/what the tradeoffs are?

Looks like it's creating a standing pressure wave and then tapping into the colder or hotter part as appropriate?

Based on the diagrams it seems like it would need a radiator or something for larger surface area?

Also curious as to how loud it is.

It uses the acoustic wave to expand and contract pressurized helium, and then conduct heat created from the subsequent pressure oscillation.

Source: https://www.pv-magazine.com/2023/01/02/residential-thermo-ac...

Which I just noticed was posted a few hours ago, here: https://news.ycombinator.com/item?id=34233719

Same question about how loud it is. Wikipedia says thermoacoustic engines work at 180db, which is the sound of a pound of TNT being detonated 15 feet away.

> 180db, which is the sound of a pound of TNT being detonated 15 feet away.

Sounds like that can be a bit annoying

Fortunately, they're only annoying for a very short time

Plus, it'll be the last time ever you hear anything annoying at all.

Not quite.

After an acoustic trauma, especially bad enough to degrade your hearing, there is a good chance you will be gifted with life-long Tinnitus.

I think he's insinuating you're getting blown up.

Guaranteed tinnitus cure

It can also stop your heart.

And warm!

Equium claims that the heat pump system is completely silent, despite the use of a speaker to generate the acoustic wave. The level of noise is reportedly lower than 30 dB – the equivalent of a whisper.

“The sound our system produces stays confined inside the core, so you cannot hear it from outside,” said Loyer.

I imagine this is possible because of better modulation of the acoustic and pressure controllers to minimize energy loss..

My traditional heat pump (using R744) claims to produce about ~37dB, and while I have not measured it I can say I would not be able to hear it over a light breeze while standing right next to the thing, let alone inside the house with a wall in the way.

To be even quieter than that is remarkable, IMO.

I'm curious, where did you get a heat pump that uses R744? As far as I know, none of the major manufacturers offer one for residential use. I'm also curious about how well it works for you.

It is super common in Japan for domestic hot water heating. It was pioneered by the government of Japan, electronic goods firms, and the power companies.

You'll see them sold under the EcoCute name. Daikin, Panasonic, and Corona (no relation) make them. They get used for homes meant to only have water and electricity hookup, called "all electric" homes.

We have this thing https://www.sanden-hot-water.com.au/specifications/ IIRC with a 300L tank. It was quite a nice upgrade from our old 1960's era 2-phase instant hot water unit that was slowly failing - cold showers in winter are not fun.

As user Danieru replied the heat pump is a a Japanese import (although the tank and rest of the system is locally made).

Same outfit in the US: https://www.eco2waterheater.com/

Probably not. A similar acoustic heat pump company (https://www.blueheartenergy.com/ourtechnology) claims 30 db, so this is probably going to be in the ball park.

Meh. This is a pressure wave. I wouldn't be surprised if tapping your finger on the table creates more pressure than that. Or hammering a nail, at least¹.

Even your TNT figure has a distance indication. Pressure decreases with the square of the distance when it dissipates as a sphere. Doubling the distance = -6 dB

¹ 20*log(k)=180 => k=1e9, factor to reach between rest state and max pressure, I think.

Is it? Doesn't Hopkinson–Cranz scaling mean that it would decrease at the cube of distance?

Tnt exploding at 15 feet is definitely still a problem for living things. With regards to the article, by confining the pressure wave to a tube you effectively keep the surface area of the wavefront constant and so dissipation is much less of an issue.

This makes no sense. Of course sound is a pressure wave - but so is being hit by a nuclear blast wave (after the initial flash). Obviously, the magnitude plays the decisive role here and not it being a pressure wave.

You're thinking of the decibels as measured from the exterior, but this likely refers to the decibels as measured at the point of constructive interference of the waveform in the chamber - ie the method of action of this heat pump. Those decibels then turn into heat, not exterior sound.

It's a really cool application of the ideal gas law: PV = nRT where the sound is really playing with the pressure (P) using sound so various parts of the chamber have different temperatures (T).

Per the article:

"Equium claims that the heat pump system is completely silent, despite the use of a speaker to generate the acoustic wave. The level of noise is reportedly lower than 30 dB – the equivalent of a whisper."

It’s been known for a long time, but sort of vanished off the radar for much of this century. I can only imagine it’s because it has applications as “mixture separators” as this webpage shows https://www.lanl.gov/org/ddste/aldps/materials-physics-appli... and so it could be used to enrich uranium (in the form of uranium hexaflouride gas), in a more robust way than the stupid legacy centrifuge technology. Thus all the interesting research on it must have been classified.

> The heat pump has a coefficient of performance (COP) of three to four, which means that it produces 3 kW to 4 kW of heat for each kilowatt of power it consumes. "We have the same efficiency as traditional heat pumps, but we have better modulation thanks to acoustic transfer"

So, no advantage from an energy efficiency point of view. The ability to modulate is certainly good, but they don't provide figures. My inverter air-source heat pump can modulate in the 1-8 kW range. How much better are they? Maybe they are more efficient in the whole modulation range. I'd love to see figures.

> Loyer said the heat pump can generate domestic water at up to 80 C.

That could certainly be an advantage. Traditional R410, R32 based heat pump are happy up to 45 C and then they really start to feel the heat (pun intended :) )

> helium at a pressure of 30 bars

I doubt that will last the stated 30 years. Gases such as hydrogen and helium are very hard to contain. Even the smallest crack or gasket problem will let it go.

> Given that its core is filled with water, it works best as a water-source and geothermal heat pump

Huge disadvantage IMO. Air source heat pumps are way easier and cheaper to install and service and work even in residential buildings. Most of the pumps I see installed around are air-source. They say that they can convert to air-source using a fan, but don't state what the disadvantages will be (e.g. wrt efficiency)

>Equium claims that the heat pump system is completely silent, despite the use of a speaker to generate the acoustic wave. The level of noise is reportedly lower than 30 dB – the equivalent of a whisper. This could be a big advantage in residential areas. Big air source heat pumps emit a lot of noise from the compressor.

> Equium is now conducting field tests for its thermos-acoustic heat pump. It expects to launch it at the end of 2023

Wold love to see some MSRP figures. Interested in early adoption in Bulgaria, Greece and the region (EU). My overall opinion is that factory made air-source heat pumps are overpriced compared to an AC unit with the same output power. That is why lots of people over here do a conversion by replacing the refrigerant-air heat exchanger with commercially available plate refrigerant-water exchangers. This however voids the warranty of the AC unit and you have to do some custom electronics to convince the AC unit that it is still and AC unit, while still providing the desired water temperature (mine works best in the 33-38C range, but my whole heating system is sized accordingly).

> I doubt that will last the stated 30 years. Gases such as hydrogen and helium are very hard to contain. Even the smallest crack or gasket problem will let it go.

Might be slightly easier than usual in this case because it's self-contained. It's not a reservoir that needs connection to the outside.

Yes, I kind of overlooked that, because the sketch has so many bolts :).

Really hoping this kind of tech to ends up in window AC+heat units soon for those of us in apartments.

The stated numbers seem comparable to a compressor based system so seems promising.

What's the efficiency compared to traditional compressors? I imagine there are a lot of opportunity for thermal energy to leak on the sides...

Edit: 20-30%, up to 40%, according to wikipedia.

I am building right now and my state (washington) recently decided no more natural gas heat, heat pumps only. That's great for the warmer side of the state but most heat pumps don't work great when it's 10 below - they approach zero efficiency the colder it gets. Blueheart seems to claim they can output 60C on the hot end when the cold end is -20C. In addition, EQUIUM seems to claim a 30 year lifetime on their acoustic chamber because it has essentially no moving parts, it's just a pressure vessel. If both of these things are true it could eventually be an advantage over heat pumps for people in cold conditions or people who are sensitive to maintenance costs once the technology is mature.

Or all the (very vague) specs could be marketing junk and it's vaporware. Neat either way.

Modern heat pumps work down to pretty low temperature, but the amount of heat you can get out at a low temperature may not be enough to stay warm with. As outside temperature goes down, you need an increasing amount of heat input. At a particular point (which depends on temperature and wind speed) capacity is exceeded, and inside temperature falls. Then you need an alternative source of heat.

Typically this is a propane furnace, but may be a resistive heater. The heat pump saves on your bill except during cold snaps, and then cost spikes.

Typically the backup is resistive, in a ducted system, it’s basically a big heater coil in the heat exchanger area. One of my two properties has one. It has never been used though, AFAIK, because it hasn’t gotten cold enough yet (and frankly, in Eastern Massachusetts, it is not very common anyway).

If you have propane/nat gas for hot water, you can use that as the backup heat -- just need a combi-boiler with a single zone through a hydronic loop in the air handler stack.

I do not, no gas line to the house. I had an oil furnace which I replaced hydronic with heat pump + resistive backup. Saving about $300/month this winter

This - we've got a brand new Daikin heat pump at 10F/-12C outside temp, it took full 24 hours to bring our place from 50F/10C to 72F/22C. A regular nat gas furnace would knock it out in about and hour and half, and at fraction of the cost.

Incidentally we're in the process of installing a nat gas tankless combi heater to address this issue - you can get a forced air set up with those.

> That's great for the warmer side of the state but most heat pumps don't work great when it's 10 below - they approach zero efficiency the colder it gets.

Mitsubishi heat pumps with the "Hyper-heating inverter" technology are above 100% efficiency down to -15℉ (-26℃). They are 200% at 0℉ (-18℃), 300% at 32℉ (0℃).

Their capacity drops from 100% at 23℉ (-5℃) to 76% at -13℉ (-25℃).

Fujitsu has similar technology, as do a few others now.

After really looking into this for my own home, I think there is some marketing BS involved. "Efficiency" is an inflated metric, it gets to a certain temperature a heat pump is going to be the equivalent of electric heat, purely expending energy to heat things up. Additionally, they have to be constantly on and cycling so they don't break the colder it gets. A gas furnace can be fired up almost in any temperature and is still very efficient. Not to mention that efficiency doesn't really tie to how exorbitantly expensive it is to run heat pumps, you're looking at +$500-800 month in extra electricity costs in some places.

I had a home in the CO mountains at 10k feet above sea level. I was looking at heat pumps since the house was electric baseboard and running a gas line was gonna cost $18k just for the line to the home.

I decided on heat pumps and was lucky enough to find a reseller of Mitsubishi who mentioned his contacts there were looking for a cold climate home in elevation that wanted heat pumps to prove their tech.

Long story short, I put in heat pumps at a fraction of the cost of what it would normally cost. Now the benefit of the mountains as opposed to Denver is it rarely gets below 0 even if Denver is -15 the mountain low might be -5ish.

Yes efficiency goes down the colder it gets but when I owned the home I never had to supplement the heat pumps to keep the house warm. It would pull 120F heat when it was -5 out. Again when its -5 natural gas is a lot more efficient but the idea is its not -5 all year. The first year I had them my electric bill averaged $650ish to $310. Also I got AC in the summer as a bonus.

There are a lot of factors involved here, sounds like you might've had a coalescence of fortuitous ones. I would not consider getting off shot freebie as the standard input cost. Also I'm assuming your home is already well insulated like most homes in places with more serious winters.

But the average house and older homes especially (in northeast esp) have poorer insulation. Heat pumps are still very expensive and for many need backup for extreme weather or require major inconvenience.

Not to mention how expensive electricity is, and the fact that it's getting more expensive.

> But the average house and older homes especially (in northeast esp) have poorer insulation.

insulation always pays for itself multiple times over. Why is rhere no financial oroduct like mortgage that wouldballow you to direct the energy saving from extra insulation into repaying installation cost ay favoirable tax-free terms and low interrest rate like mortgage?

There are, in fact perhaps a bit too much, it has resulted in lots of insulation and heat pump scams lately (though perhaps not enough enforcement ?)

See also how the real estate sector was whining in the recent years about the (quite mild !) new insulation laws, seemingly only caring about their short term profits. Well, hopefully they have shut up now (or maybe not, with, now that we ARE in the predicted crisis, serious laws coming up, and at the same time, the real estate bubble popping).

It's going to get worse now because the fed govt has a rebate to install heat pumps, I'd expect the same treatment people get for solar to come to that now, lots of companies cold calling trying to sell more of a financial instrument than actual product. I was really looking into one, and it was impractical due to weather but also not many local contractors were trained and servicing them, I expect more grifter types to pick it up.

That does sound like something places should offer. I know some ESCOs and providers offer like free thermal imaging of your home. While insulation is relatively cheap, often the worst culprits are poorly insulated windows and any penetrations to exterior. Those are much more expensive, window replacement can easily run 20k.

You can use a HELOC for insulation upgrades, just like any other home improvement project.

If I just bought a house with shit insulation with mortgage, is HELOC gonna help me?

Why did you buy a house with shit insulation?

Yeah, that depends on your situation... I recently got into a discussion with someone complaining how her heating bill doubled in a year, so she has to skimp on heating or cooking because she cannot afford it any more.

She has gas heating, while I have electric (which got something like +75%, but starting from a lower baseline), and I don't even have a heat pump !

But then my insulation is average (and I haven't even started heating yet, though to be fair should have for at least one week, this winter is insanely warm so far), while hers is supposedly very bad, probably one of those apartments who have been recently announced will be illegal to rent soon.

And she got furthermore protected by the government which froze gas prices - someone will have to eventually pay those ×5-×10 bills !

In the medium-long term, methane is probably less viable than electricity, which is easier to transport and can come from a variety of sources including 60% efficient gas turbines.

I agree with last point, and you can see some effects of that now where they are no longer building underground gas lines and such for full new constructions and developments in some places. However, aging and unreliable infrastructure which will never be replaced until it's completely destroyed will mean that nat gas will stick around for a long time.

I’m surprised you needed AC at 10k ft. I have a cabin south of FairPlay at 9200 ft and the high temperature for the year has never exceeded 81 F.

Good to hear on the heat pumps though. I’m planning to eventually replace the propane boiler with them.

So the home is southern facing and was full of windows on the southern side. So even with windows open/shades down the heat from the sun would still radiate in.

When I bought the home I had a company come to help me plan the heating and I don't fully understand the science but the home is built to keep heat in with the windows and no attic.

I'm confused, are all your temperatures in Celsius except the 120F (~50°C). I assumed the -5 was -5°C but the use of F later suggests it could be -20°C.

all the temps are in F.

The hyper heat can pull 120Fish heat down to -15F

> Not to mention that efficiency doesn't really tie to how exorbitantly expensive it is to run heat pumps, you're looking at +$500-800 month in extra electricity costs in some places.

You might be an order of magnitude higher than reality here.

I do live in the French Alps (relatively cold) in a 160m2 house warmed with an heat pump. My bill is around 600-800€ per year, not per month. My house is from the 1970s with an average insulation from the 80s

I do not see how you can get 600-800$ per month, excepted if you do live in a -25˚C climate and in a house insulated with a sheet of paper. But then you will probably get an even worst bill with a gas boiler.

> But then you will probably get an even worst bill with a gas boiler

Quick google shows that electicity in France[0] costs roughly 1.6x more than natgas. For Washington State this ratio is around 2.45x.

Eyeballing this graph[2] that corresponds to breakeven outside temperature of <-20℃ and -8℃ respectively for 40℃ output (~-18℃ and 0℃ for 50℃).

[0] https://www.globalpetrolprices.com/France/ [1] https://www.bls.gov/regions/west/news-release/averageenergyp... [2] https://support.sefaira.com/hc/en-us/articles/115000249971-A... -> scroll down roughly 2/3.

> Eyeballing this graph[2] that corresponds to breakeven outside temperature of <-20℃ and -8℃ respectively for 40℃ output (~-18℃ and 0℃ for 50℃).

Interesting perspective, thank you. Considering that the average winter temperature in Seattle (Washington) is around 3-4˚C [1], it is far over the breakeven.

It is even more true in my case: my system is is a water-water geothermal type. They do maintain maximum COP (4-5) and maximum power independently of the outside temperature. They are perfect for cold climate.

For the little side story: My heatpump has been installed in 1987 by the previous owner of the house and I believe he was truly a visionary.

Nobody was talking or even speaking about heat pump at that time. From his own words: people of the neighbourhood took him for a mad-man when he said in the 80s he would warm his house with the cold water from the river. Facts are that his system is still running 35 years later and provided a cheap, reliable and low carbon source of heating for over 3 decades.

[1]: https://weatherspark.com/s/913/3/Average-Winter-Weather-in-S...

Worth noting that Washington state is not just Seattle - we over here in the eastern side of the state get much, much colder!

>Aaaacshually...

100% efficiency on a heatpump is really, really, really bad. It's effectively like warming your house with electric baseboard heating which is very expensive, 4-5x the cost of natural gas in my area. Thus why I said they don't work great when its 10 below. Because they don't work great.

Anecdotally, a few people I know who moved to New England (where it can get down to -20F at night, though rarely) have installed heat pumps and been happy with the performance through the past few winters, though I don't know which models they bought (one mentioned the Mitsubishi H2i).

I believe all of them also have a woodstove for backup heat and general coziness, but no separate fossil fuel backup.

Yeah, we live in northern New England; (air source) heat pump + wood stove is getting to be a very popular combination around here.

do you live in a well insulated (net-zero or passive home)?

The solution to that is to not use an air based heat pump but to drill down into the bedrock, well past the freezing depths and circulate water down the hole and take warmth from there. This is quite a bit heavier on the investment side but a lot more efficient during cold weather.

I would be very cautious with declared lifetime of non-existing things, all Equium (and seemingly the other player Blueheart, that state a much more conservative 15 years lifetime) have right now are laboratory prototypes.

If you check the Blueheart "About" site here:

https://www.blueheartenergy.com/

they have nice pictures of the various prototypes and of the (supposedly final) product, you can appreciate at a glance how different they look, and it wouldn't be the first time that expected lifetime (estimated on prototypes) results vary for the industrialized product.

According to a different article the COP of this heat pump is between 3-4. However, Thermoaccoustic Heat Pumps have some advantages that you can also find in their press release; because there is no refridgerant, only the air medium which is Helium in this case, you can operate them down at much much lower temperatures without loosing much COP, same in reverse (they claim -15C to 50C). And because there is few moving parts (only the acoustic coupler) they can have an immensely better lifetime than a compressor that needs oiling and maintenance (Equium claims 30 years service life).

They aim for fairly small heat pumps from the looks of it, so this might be something targeted at people renting flats. Something to replace the gas burner for most of the winter.

Can anyone tell me why they use Helium rather than say Nitrogen?

I thought I read somewhere that we are running out of He.

We're running out of cheap helium. For applications like this, I'm sure it'll be fine.

Helium is a more effective heat transfer medium with lower molecular weight. Hydrogen would be more efficient but it tends to cause issues with the containing material and leaks.

From this [0] NPR piece:

Helium is the only element on the planet that is a completely nonrenewable resource.

On Earth, helium is generated deep underground through the natural radioactive decay of elements such as uranium and thorium. "It takes many, many millennia to make the helium that's here on the Earth," says Sophia Hayes, a chemist at Washington University in St. Louis. The helium seeps up through the Earth's crust and gets trapped in pockets of natural gas, where it can be extracted.

Like hydrogen, its immediate predecessor on the periodic table, helium is lightweight. But unlike hydrogen, it doesn't readily combine with other elements. So, once helium reaches the surface, it can easily escape the Earth's gravitational pull.

Other resources, such as oil and gas, may turn into pollution or be difficult to recycle. But only helium physically disappears from the planet. "It's the one element out of the entire periodic table that escapes the Earth and goes out into outer space," Hayes says.

[0] - https://www.npr.org/2019/11/01/775554343/the-world-is-consta...

FTA: Because helium remains a gas until -200 C, we can achieve higher temperatures inside our heat pump core

N₂ boils at −195.8 °C, but that will be higher at 30 bar.

Next question: why do they need gas at lower temperatures to achieve higher temperatures? Do temperatures inside that acoustic wave vary that much?

Probably because the higher delta allows for higher power density and keeps the device reasonably small ?

To improve the COP you need a gas with a high ratio of specific heats and low Prandtl numbers. The Prandtl number is the ratio of viscosity to thermal diffusivity. Helium works fairly well for this, though adding xenon, argon or krypton improves it even further.

Really cool to see a company getting this in the market. I'm surprised though to see a standing-wave device instead of a traveling-wave device.

I haven’t seen a mention so far, but 30 bar pressure isn’t that big. Scuba diving uses helium (wellC helium and oxygen) at up to 250 bar (in small cylinders, 10-12liters) with no issue whatsoever. The cylinders aren’t even that big or heavy (for a heat pump).

I wonder how efficient it is at lower temperature outputs. If we can see much higher COP at lower temperature gradients, then it would be even more impressive.

A much larger COP at 20C delta would be more effective for heating in moderate climates.

Every time a story like this pops up I find myself solely scanning comments for the critical flaw in the technology. Pavlovian dashed hopes response.

This is awesome! No wait, helium would cause this super-efficient heat pump to cost more than it is worth and put a strain on areas where helium is needed, like MRI machines, which are already having issues due to the increasing rarity of helium. Couldn't they have used argon or nitrogen instead of helium?

Can this run in both directions? I’m eager to explore radiant heating and cooling (in like a 5-15 year time frame) and wondering if it might be good for that.

yes, one reductive way to see it is that they physically move the cold molecules on one side and the hot ones on the other side. So now wether you want to steal the hot or cold side to bring in the house is "your choice" (quotes, because the temperatures involved have to be useful for you to want to bring them in). The side you don't want to bring in the house will soak in the outdoors.

One part to the heaters, the other to the fridge or freezer. Win-win in winter.

How does this compare to the energy efficiency/cost of gas-powered water heater?

I don't see how you can compare energy efficiency between something powered by electricity and something powered by natural gas. They're two entirely different energy sources. The electric one doesn't involve putting more CO2 into the atmosphere, at least directly. And cost is completely variable, as electric and gas prices both vary wildly depending on location and time (gas became much more expensive in the last year).

Typically much better efficiency since a gas heater is only 100% efficient, maybe up to 200% relative efficiency if the electricity comes from a faraway gas turbine.

Cost difference is going to vary by an order of magnitude (and more) depending on the local conditions :

https://news.ycombinator.com/item?id=34242237

I wonder why Helium instead of much cheaper Nitrogen?

Is this the same tech used in James Webb telescope?

> Fun fact is that the JWST cryocooler operates on a similar principle (although the implementation is quite different).

as per u/alexose in this thread.

Critical issue with this technology it only really works well with helium.

no, though helium does have real advantages

hydrogen is actually even better iirc

but air works too

Different issues with that, but maybe no worse than a bottle of kerosene.

a bottle of kerosene might be 500 g, or 21 megajoules according to https://en.wikipedia.org/wiki/Energy_density#In_chemical_rea...

but 2 ℓ of hydrogen (i don't know how much you'd use in a residential thermoacoustic cooler so that is a guess but probably the right order of magnitude) is only 0.02 megajoules, a thousand times smaller

otoh the kerosene doesn't form an easily detonated high explosive if it mixes with air, and the hydrogen does, and 20 kilojoules can still be plenty fatal in an explosion

Seems like N2 would be a better choice unless absolute molecular weight is important. Helium is hard to keep confined.

Reading up a bit, it seems like this has to be a traveling-wave device to get the efficiency advertised: standing wave devices seem limited to a Carnot cycle, where a traveling wave device can operate a Stirling cycle.

Absolute molecular weight is important. Can't remember why off-hand but if I recall correctly there's a pretty substantial efficiency hit from using heavier gas molecules and conventional Stirling engines have a similar issue.

Could you elaborate on that? I'm curious and thermodynamics was a while ago...

Wikipedia will be more helpful here than I can be.

Yeah a large scale solution involving helium will not scale. Helium cannot be produced by any process other than hydrogen nuclear fusion, and has to be harvested in nature from natural gas wells. Using it in nuclear reactors is one thing, but at home?

Since most of the worlds natural gas is in Qatar and Iran, the world will just have a helium resource crunch if this becomes widespread. Maybe a better working gas to use would be ammonia or desiccated propane.

Maybe the ultimate solution is to have neighbourhood heating/cooling units that serve multiple and pipe hot/cold water to them.

This is a common misconception. Helium and hydrogen leaking into ultra-high vacuum systems is a problem since even trace amounts spoil the vacuum. The leakage out of a storage vessel is completely negligible.

This is not an issue at all. Helium is inert and relatively cheap. Filling the device with a couple hundred liters will cost a few Euros.

Until someone shows me a very detailed video how this works I wouldn't put it in my house. It looks like a nuclear bomb.

Also, you just _know_ people would just defer maintenance on this.

But high-pressure cylinders of propane do not?

Who said I have propane tanks at home?

Does this mean I now have a good excuse to buy noisy toys for my grandchildren?

LOOL this is the best prank i read in months. Now they will get funding offer by some fat ass government-sponsored EU fund and then publish this as a warning on how you can steal almost infinite money by riding green hype and bullshitting people who didn't go to high school but were put in charge of million euro decisions.

Come on people they are even giving you dead simple hints to make this as laughable as possible, mentioning a "Hi-Fi (High fidelity)" speaker - as if anything but a single-frequency acoustic wave might matter here.

> The heat pump has a coefficient of performance (COP) of three to four, which means that it produces 3 kW to 4 kW of heat for each kilowatt of power it consumes.

This is setting off some massive BS alarms in my head. Why is this not violating conservation of energy?

Heat pumps rearrange existing heat in the environment, they don’t release it chemically by burning which is inherently <100% efficient.

The wording is bad. It’s moved the equivalent of that energy.

Technology connections did a good video on this.

https://m.youtube.com/watch?v=7J52mDjZzto

This just means that you are moving heat energy from one resovoir to another. The total amount of energy the system releases is the energy moved AND the energy used to move that energy. COP is calculated by dividing the amount of heat moved by the energy used to move that heat. In short no violation.

This is a common headscratcher in the heat pump space. They're taking advantage of a thermal gradient to get more out than they put in. Very much like driving downhill, as I understand it. If you put an air conditioner into a closed system, you can't beat Carnot efficiency. But if you're allowed to dump/absorb heat to/from the environment, the coefficient of performance measures the heating/cooling on the control side versus energy input -- which is allowed to go over unity.

https://en.m.wikipedia.org/wiki/Coefficient_of_performance

(I'm no authority here -- I only bought a heat pump and had the same reaction as you)

It’s cheating! The extra energy comes from the environment. It’s much easier to steal the heat energy out of the outside air (or out of the ground in colder climates, because it stays warmer) than to create the heat yourself.

Producing heat can only be COP=1 if it’s 100% efficient, but you can use the same amount of energy to move three, four, even five times as much heat to or from the outside (moving heat the opposite direction is the way air conditioners work).

This is not really a downvote-worthy post, I upvoted it. You are right to sound your BS alarm, but as others have described, heat pumps are 100%+ efficient by cheating. So, not really, but also, yeah they are.

If there was a massive alarm going off in my head and I was already at my computer, I'd probably take 2 mins to Google "how does a heat pump work". But I appreciate not everyone thinks like that.

Heatpumps are an extremely widely deployed technology by now (I have one in my house, so have everyone I know); this is an article about inventions in heat pump space, and the post is sceptical about the concept of heat pumps.

Kind of like a post about a new kind of airplane getting a comment saying that the concept of flying makes their BS alarm go off. Yes, flying is a bit "magic" and seems to defy the laws of gravity....

It's a misunderstanding of energy conservation. It's not cheating if you count all the energy in the system.

Heat pumps do not generate heat (well, only as a side effect of moving parts). Heat pumps compress gas. By using a compressor, they cycle gas between a low pressure chamber and a high pressure chamber. The low pressure chamber is outside, absorbing heat from the surrounding air. It is pumped into the high pressure chamber using the compressor, turning a large volume of cool gas into a small volume of hot gas (conserving energy). This hot gas warms your water or air. The now cooler, but still high pressure gas is leaked into the low pressure chamber, where it expands turning a small volume of warm gas into a large volume of cold gas (conserving energy), and the cycle continues. This is how you spend 100 joules of electrical energy to move 300 joules of heat energy from outside to inside and 300% heating efficiency.

The thermo-acoustic ones are using sound waves instead of a compressor, but the same principle.

Heat pumps do not generate any heat at all instead as the name applies they move (pump) heat.

It just happens that physics allow you to move 3 or 4 kW (maybe even more in future) of heat energy from outside air inside with 1kW of energy and thus the COP. And if you run the loop in reverse you get what is traditionally called air conditioning.

How traditional heat pumps do this is with a refrigeration cycle just like your fridge or freezer does basically by compressing and decompressing a gas.

What a heat pump does is move heat from outside your house to inside your house (hence the name). You can do this for free if the outside of the house is warmer than the inside (just have a thermal conducter). If the outside is colder though, it costs energy to move the energy - you're pushing the heat "up" the temperature gradient.

[Of course, this is a heat pump used in the 'heating your house' use case - heat pumps are more general. Fridges and air conditioners are also heat pumps that use energy to move heat from a cold place (fridge/room) and release it in a warmer place (the outside)]

What you actually care about is entropy for these systems. Conservation of energy doesn't care whether the energy is inside your house, or outside your house.

0 = change in energy inside + change in energy outside + added energy

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