ElKaWe – Electrocaloric heat pumps | Hacker News Reader

ElKaWe – Electrocaloric heat pumps

fraunhofer.de

177 pointsdanans92 comments

To try and understand it I just skipped through this lecture:

https://www.youtube.com/watch?v=-d4NAEPZrbg

To a layman like me, the most interesting bits start at: 6:14 and 37:36. If you're interested in the materials (they're perovskite crystals) it's at 22:45.

My explanation as a total layman: There are materials that when you apply an electric field to them they almost immediately heat up. Then as you keep the field on them they cool down again naturally, and if you then remove the electric field they cool down quickly. So you with electric fields you can make the material do a pretty wild temperature swing.

Then the next trick is to extract that temperature differential from the device. You could imagine a container with a fluid and the device in the middle, a hot side on the right and a cold side on the left. As you push fluid to the right you heat up the device, and as you push fluid to the left you cool down the device. This will over time sort of ratchet the both sides to greater extremes. Even simpler they also made a "slapper" which simply puts the device on a little motor actuated arm, and it slaps the device to a load whenever its cool, and then to another load when it's hot.

Other (to me) cool detail is that they got Murata to manufacture these devices as MLC's, so it's just your typical Murata MLC capacitors but with these electrocaloric material layers.

edit: also at 44:00 he shows a slide comparing this technology to others, and it shows that even though it's more efficient than vapor compression it's less efficient than acoustic, although they're both very efficient. So I guess the big question is going to be is if this is going to be more practical/economical. From what I've heard there's a bunch of companies already moving forward with manufacturing thermo acoustic heat pumps so those are definitely further along.

> more efficient than vapor compression

This has a lot of asterisks around... Vapor compression has 100% of the theoretical (ie. carnot efficiency), as long as you use the correct type of compressor (ie. isothermal) and use an isothermal expander instead of a capillary tube.

Unfortunately, isothermal compressors don't exist, however approximating one with a multi-stage regular (ie. Adiabatic) compressors interleaved with radiators gets pretty close to it.

Turns out that in current systems, the extra piping and complexity isn't worth it. But when energy is expensive (if people start taking carbon emissions seriously) and manufacturing is cheap (due to all the parts being mass produced), it becomes worth it.

it becomes worth it when the heat pump makes it so that i can live in my house without getting heat stroke and dying :)

Or die of starvation because all income is going to winter heating bills!

actually, the reason why I need an air conditioner so badly is because my body naturally generates enough heat that I don't need a heater in winter. I also usually don't need a coat in below-freezing temperatures unless I'll be out there for longer than 30 minutes.

Commonly-accepted indoor temperatures of 70-78F are far too warm for me, I need closer to 60F, ideally below. I have to open up and modify my air conditioners so that they won't shut off near those temperatures, because from the factory they will refuse to make the room cool enough.

They're talking about whether it's worth it to go multi-stage, not to have the device at all.

The curve figures he show in video at 14:03 looks like the curve of memristors.

This topic feels to me like a moonshot attempt [0]. Institutions like this, live on the EU handouts [1] (in fact I applied with my company together with Fraunhofer a few years back on a EU subsidy). Meaning, the fact it is subject of investigation does not imply this will proof to be a valid path to follow.

How I see it the following has happened. EU bans f-gases. The industry had objections and EU sets up a program of subsidies to search for alternatives. And there you have another political argument to ban f-gases in the first place. A mostly foreign industry (China, Japan, US) is suddenly a massive transition market where we (the EU) are engaging in massive investments and subsidies. It does not hurt the EU to stir this up a bit giving EU industry a better position.

[0] https://en.wikipedia.org/wiki/Electrocaloric_effect

[1] BTW I agree with these 'handouts' and the existence of institutions like Fraunhofer. As said I also cooperated with them on a similar package and with all fundamental innovations, it is highly uncertain if it will become a success.

This seems like a Fraunhofer internal project so it seems to be from the base budget they can freely invest into research (still tax payers money and with a political edge to it)

The general criticism to the European subsidiaries applies though to all the 'competity' research funding that not necessarily leads to go to market approaches . But this IMHO is a bad example.

It puzzles me how people can ignore stuff like DARPA while simultaniously argue against stuff like publicly funded Fraunhofer research.

Yes, the US military industry complex along with DARPA funding etc., seems like a huge subsidy exercise. There are also these weird rules in these grants as well, i.e. you have to fly US airlines (the irony obviously is that the US often strongarms smaller economies into abolishing these rules as being "anti-competitive/free-trade".

To be honest the way I read it the funding on this sounds like it is mostly about material science. I think this is well spent money as it expands the possibilities of what we can do beyond the intended target application of electrocaloric heat pumps.

A big fraction of what we do better today than say, 4 decades ago, is due to improvements in material science, not because we are more intelligent or better planers (although, some of the software aided planning that happens on big projects nowadays would not have been possible back then).

The EU is a tiny part of Fraunhofer funding:

General Finances:

https://www.fraunhofer.de/en/about-fraunhofer/profile-struct...

Research Funding Figure:

<https://www.fraunhofer.de/en/about-fraunhofer/profile-struct...>

EU is 93 Million Euro out of a total of 2,518 Million Euro.

That vast majority comes from German governments and ministries, both in the base funding and through project grants. Then the next major block is R&D done at Fraunhofer funded by industry (723 Million Euro). EU Funding is often as much about the prestige as it is about the projects.

IIRC correctly Fraunhofer can not apply for the majority of EU funding as the main party, but instead they are a partner on somebody else's grant.

Unless they are partners as subcontractors, this would still show up as EU-based funding here. And they can definitely participate in normal grants as partners. Not sure what exact rule you have in mind.

"Unless they are partners as subcontractors,"

Well that's the loophole, isnt it?

A loophole for what? Fraunhofer has no incentive to hide that they get EU grants.

On the contrary, these grants are extremely competitive and prestigious.

Exactly! Some people on here have weird ideas.

For context: Fraunhofer employee here.

Fraunhofer is a not for profit organization, consisting of around 75 independent institutes. Our income comes from three sources: (1) publicly funded R&D, for example EU grants. We apply just as everyone else, so we compete with universities and private companies. (2) Industry grants. This is where the “applied science” of our mission statement comes into play. These grants are mostly from SMEs, but we also have huge industry grants. And finally (3) the base funding from the Germany’s government. The idea is that common cost like buildings and infrastructure is covered by the base funding.

The base funding depends on the ratio of income from (1) and (2). About 40-50 percent should originate from industry (2). If an institute deviates from this, their base funding will be reduced. Bottom line: There is a strong incentive to do research, but also to transfer that knowledge to industry partners. Failing to do both will reduce the base funding. Its a delicate balancing act, for each institute.

Oh come on we owe Fraunhofer at least psychoacoustic compression, the basis of MP3 and most current audio formats. It was also a moonshot project at the time. It's like complaining DARPA lives on the govt handouts: of many things that to it's among the least problematic.

The real handout here is who benefit$ from the publicly funded moonshot tech that makes it into real world applications eg smart phone components

I was able to download and listen to sound tracks over my 33.6kbps link back in the 1990s, so I definitely benefited.

If memory serves me right they had a project to set up digital radio in Africa so low-bandwidth that the spectrum would have room for stations in even the most niche languages. Languages on the edge of extinction, to help those languages survive. No idea if they ever helped a single language, but they sure weren't without impact.

(I suppose the project was one of many related to audio compression, but it was the one I heard a presentation of, to highschool-age youth in the style of "this is what a career in science might look like")

???

Wasn't MP3 patent encumbered for decades?

T-thanks Fraunhofer ...

I blame all the people who didn't invent psychoacoustic compression so that FHI couldn't patent it.

To be fair patenting publicly funded stuff is not ok. All IP produced with government money should be public domain.

There is an alternative argument that government should be treated like any other financing partner and recieve a share of ownership in such patents with the revenues used to fund further works, thereby driving the majority of funding to things which have the greatest consumer benefits (proven through the value of patents).

There's ways that leaves us with some innovations left by the wayside though, so a mixed system would likely be best to ensure the best net outcomes

Also acceptable... But the government should get something out of it if it was on the public dime.

Exactly my point, thanks,

This doesn’t appear to be funded by the EU. The EU usually makes it a requirement to indicate if a project is funded by them. The Fraunhofer society itself gets its funding primarily from the German federal government. Of course they also often apply for EU grants. I have hard time understanding how this comment about EU funding is in any way relevant to this submission.

Accusing public research institutes of "living on government handouts" seems odd. I think a better address for critique for funding (if you think the idea is flawed) would be whatever instrument granted it.

The major thing I see wrong with Fraunhofer is the patents side, but that's another kettle of fish. (It's just as much the fault of the policymaking that use patent grinding as a benchmark for "innovation")

I don't accuse them of living on gov handouts - I am just pointing to that fact to set the correct expectations. This funding is particularly necessary as the research is too fundamental for commercial parties.

Who else would fund basic research that will likely not yield any profits in the near future? Obviously most basic research is funded by governments.

Bizarre criticism and some vague geopolitical arguments that are hard to parse.

This is publicly funded research in an (at least nominally) valid and important technological direction. While tech is unlikely to solve the sustainability problem by waving a magic wand, it wont hurt to create as much room as possible.

Fundamental research is always a "moonshot". Practical, implementable, commercializable technologies don't grow on trees.

So I looked around for real figures of merit on these things - efficiency is but one. One thing I noticed is that every press release failed to mention the heat flux of these devices.

Gscholar to the rescue.

\DeltaT = 5 K and a max Q of 135mW/cm^2 for a research device from MIT. Note, max Q implies \DeltaT of 0K [1]

On digikey I pulled up the first data sheet I could find. [2] https://www.cuidevices.com/product/resource/cp60.pdf

The CO60133 can pump 10 W @ 10K. Max Q is 12W from an Sa of 2.5 cm.

Or a Q of 4W/cm^2 @ \DeltaT of 10K. Or 30 times better for the Peltier device.

These devices are cool, but they're not even remotely powerful enough to replace Peltier devices, never mind traditional refrigerants.

[1] https://fisherp.mit.edu/wp-content/uploads/2020/10/129.full_...

[2] https://www.cuidevices.com/product/resource/cp60.pdf

They are really unpractical at the moment, but so were peltiers and solar cells when they first started out. Now those technologies are robust, effective, and practical.

With enough research, perhaps these will also be practical. I think a MEMS implementation with chip scale devices might fit the bill if suitable materials can be discovered.

Since these are basically capacitors, If we say Dt is 1c and the single cycle density is low, we might be able to use MEMS to get a MHz cycle rate and layer them 100 thick like NAND. Then you’ve got an extremely high thermal flow (millions of cycles per second) and 100c Delta—T in a device that can be produced at chip-scale.

Peltier devices can’t unlock this process, since their base efficiency is so dismal that you would just be creating a heating element.

I don’t know if any of this is possible with -this- device, but it is meant to be an example of how modern technologies can create unexpected outcomes from humble processes, when the efficiency of the granular process is high enough.

If this could leverage MEMS in a similar way to how massive parallelism revolutionised power MOSFETs, it would be a fantastic tool for humanity.

The problem is that your linked peltier consumes 22.8W of power to pump those 10W. That is a horrible efficiency, and completely useless for most applications.

At that point you're probably better off with plain old resistive elements when trying to heat, or literally anything else if you are trying to cool.

Being limited to a small temperature difference and power capacity per area isn't that big of a deal when you stuff a whole bunch of them together, especially considering the goal is to replace traditional building-sized heat pumps. Needing tens of thousands of them only matters due to cost - and that's way less of an issue when it is more efficient than the alternatives.

There are use cases where a 30x increase in surface area would be fine. For example, 10W of heat pulled out of an insulated cooler would do a good job, and you could easily dedicate 100 cm^2 to the device.

Of course it would have to do that at a much larger delta T than "near zero".

The phonetic form of the title maps to LKW - LastKraftWagen (truck) in German.

Or Leberkäsweckle.

Coming up with (at least a bit) fun names for grant applications is a small plaster on the pain these applications involve. If the money actually comes, the fun name has a good chance to stay, as everyone has gotten used to it.

When I read the title I thought no way this is not from Germany. It's a nice pun, I like it.

Lots of interesting work being done there. Here's a rival idea, based on deforming metals: https://www.ipm.fraunhofer.de/content/dam/ipm/en/PDFs/report...

What's the news in this release, according to another page [0] this ran from 2019 - 2023; Or does this announce further collaboration?

Am I overlooking a PDF or detailed report?

[0] https://www.iaf.fraunhofer.de/en/researchers/electronic-circ...

It's not a press release; it's part of a section on their website that lists their current light house projects and provides some convenient pointers to the different parts of Fraunhofer that are involved and some contacts.

Edit. Here's a recent news message related to the same project: https://fagenwasanni.com/news/fraunhofer-researchers-achieve...

on https://www.deutschlandfunk.de/effizientere-waermepumpe-frau... is an interview with the lead scientist, Dr. Kilian Bartholomé. Summary: they claim a possible COP of 5-6, a lab implementation just now yields a temperature rise of 1K, it will take some years to find suitable materials. [Sidenote: "ElKaWE" could be a pun, as its pronunciation is the same as "LKW", the german word for truck

A COP of 5 is meaningless if you don‘t know the theoretically possible maximum COP in an application scenario. But thanks for the pointer, DLF interviews on scientific topics are usually quite good.

I'm not getting it. Does someone have some diagrams?

This line is confusing me: "If the electric field is now removed, order is reduced and the material cools, also in accordance with the laws of thermodynamics." How is decreased local order an decrease in local heat? I think heat engine-like diagrams would help me here.

I'm also a layperson, but to my understanding when order within the electrocaloric material is allowed to reduce it means that the material can now absorb unorder from the environment, i. e. heat. Things that absorb heat are called "cooling".

Interesting. This is something different than the thermoelectric effect, known from the Peltier element, see https://en.m.wikipedia.org/wiki/Electrocaloric_effect

A similar effect you can try out at home: expand a rubber band, wait a few seconds, then touch it with your lips and release the tension.

of course, someone on YouTube tried their hand at building a heat pump using this effect: https://www.youtube.com/watch?v=lfmrvxB154w

Very cool, thanks for the link!

I’d be really interested to see a write up on the particular materials and how much current is required or if it’s simply a Delta V that achieves the effect. It’s been many years since I was in college, but my mind cannot comprehend such an action generating a considerable amount of heat.

Well according to an interview with the group leader at Fraunhofer, they achieve 1 Kelvin in the lab, long way to go. Of course some current has to flow in order to establish the field and as long as the polarized atoms in the material are aligning (the thing is a capacity, the ceramic material a dielectricum).

I'm skeptical, how do you separate the hot and cold reservoir in such a system? Afaik peltier elements have bad efficiency cause of this. With liquid/gas you can easily have split systems, giving these heat pumps much higher efficiency.

It sounds like they are physically moving the element between a hot reservoir and a cold reservoir. Apply the field, and move to the hot side to disapate heat. Then remove fron hot side, release the field, and absorb heat on the cool side.

That should allow for pretty good separation between the two. I suppose rather than actually moving the element, you can use valves and liquid reservoirs to either let the cold reservoir flow through, or the hot reservoir.

That was my most generous interpretation too, but when I read it I didn't see any details on whether or not this is solid state. I'd be suspicious of a high performance solid state heat pump.

IIUC they're looking at ceramics.

Honest question: can there be ceramic fluids?

You're right, but then the heat capacity of the material would have to be low or the electrocaloric effect would have to be very strong for this to be more efficient than gases. Still skeptical.

Edit: And what about the surrounding material, pipes and stuff. They are now cycling between hot and cold too, wasting energy.

You plumb two pipes through the element that are completely separate. Then you enable or disable flow through the pipes depending on the state of the element. No mixing, no loss to the surrounding material. Though this depends on good heat conduction within the material.

Presumably though, the switching speed would need to be rather high on both the electrical field and the material. But if the bulk material is cheap enough that you can make it quite massive for a low enough price, I could see it work.

It is not Peltier. But seems like solid hardware indeed.

The efficiency of heatpump is 1.0 thermodynamics. Ie yes there is a transition in fluid / gas, but the efficiency is not because there is a split. Monobloc heatpumps are common, and have similar efficiencies compared to split units.

It stood out to me that this website states, as a matter of inevitable and accepted fact, that the use of refrigerants will be banned from the EU in some kind of short timeframe. That seems a bit insane on its face unless I am completely out of touch with EU politics since I am in the USA. Refrigerants are extremely useful and are capable of offsetting their greenhouse effects by so many orders of magnitude it isn’t even worth discussing. Heat pumps are finally taking off and have the potential to throw out fossil fuel heating in most of the world within the next decade. Why would anyone want to stop that?

I think only the environmentally unfriendly refrigerants will be banned.

The EU regulation is about industrial use of fluorinated greenhouse gasses.. I don't think that will ban other refrigerants

Yeah you can use propane, isobutane, ammonia, or CO2. The first two are flammable, the second is both. And CO2 requires higher pressure.

They aren't as nice from a safety or operations standpoint but ain't the end of the world really. Although they are now way cheaper than fluorocarbons.

The CO2 heatpump needs more than 150 bar, like having a small OceanGate in your attic.

More like having a medical oxygen or welding gas tank in your attic (except with a much less reactive gas).

Or like a convenience whipped cream dispenser. Quantity and geometry certainly makes one more volatile than the other, but the number alone isn't all that far out.

Huh? Propane is quite easy to deal with, though? Besides being flammable, but that merely means you have to ensure it gets sufficiently diluted in case it feeds indoors, doesn't have an opportunity to asphyxiate occupants, and isn't eager to burn the house down in a typical catastrophic malfunction.

Unlike fluorocarbons, you don't need to worry about leaks beyond the flammability/asphyxiation aspects, and could conceivably flare excess/contaminated charge off (just to prevent an explosive food from being able to form), with no environmental worries beyond the burning/flaring of fossil fuel (and whatever contamination the oil contributes). Might not be legal in a particular jurisdiction, but I assume that's a product of fluorocarbons being the norm and them being an environmental issue to leak, supporting a blanket ban on leaking any.

Almost reminds me of the whole parallel debate around nuclear...

Better than fossil fuels but has some of its own (comparativly smaller) waste problems, and its also getting phased out.

> and its also getting phased out

That's disputable

It seems that refrigerants get a lot of bad press. In particular in heatpumps. Nobody seems to really cares about the gasses used in refrigerators or aircos in cars.

Obviously, it is good to ban particularly bad gasses. Freon because of its negative effect on the ozon-layer. The same way some gasses have a very large greenhouse effect and can be replaced by gasses that are better.

If a new technique becomes mature and it has obvious benefits over the existing solution, that it not a bad idea to prohibit the old, poluting way.

> Nobody seems to really cares about the gasses used in refrigerators or aircons in cars

I believe Project Drawdown selected refrigerant managament as one of the top climate change mitigation strategies:

https://drawdown.org/solutions/refrigerant-management

Ozone-depleting CFCs have been banned world-wide in the 90s, and some HFCs with large global warming potential have been banned for use in cars in both the US and the EU.

I assume the relevant text is this:

In cooling technology, the gradual ban on refrigerants under the European F-Gas Regulations makes alternative, refrigerant-free technologies more desirable.

That seems like a reasonable statement. I'm not sure why you took that to mean a "short timeframe" or a complete ban on all refrigerants.

Edit: here's a link with some information about the F-gas regulations.

https://climate.ec.europa.eu/eu-action/fluorinated-greenhous...

Fluorinated refrigerants. The GHG effect of these is far, far worse than CO2, which means we'd need to see numbers for

> capable of offsetting their greenhouse effects by so many orders of magnitude

It's the crazy persistent halo/fluorocarbons that will be banned, things like pentane will be ok...

Yes, it is an interesting move of the EU [0]. The manufacturers of heatpumps are already lining up alternatives: mostly Propane (R290) but also CO2 (R744).

How does that align with the billions being invested in Hydrogen, a gas with a GWP of 11? This stuff will leak to the atmosphere at a massive scale soon, dwarfing the tiny tanks of f-gases.

[0] https://ec.europa.eu/commission/presscorner/detail/nl/ip_22_...

Yep there are already multiple heatpumps on the EU market that work with Propane. Interestingly, they are also marketed as "high temp", capable of emitting 75C water to drive normal aluminium radiators, similar to how a condensing boiler would.

In part this is due to how this still has a commonly accepted pressure ratio (vapor pressure at condenser:evaporator ought to be ~10:1 for fridge-like compressor designs to be happy), and in part because having the propane equipment outdoors and only interacting with water/water-glycol-mix for thermally connecting to indoors makes the safety aspects far easier. It's now hard for propane to sneak indoors, form a mildly concentrated puddle, any blow up from static discharge at the next opportunity.

Propane/air heat exchanger are normally dangerous due to difficulty of dealing with a leak even if you use a sensor to detect leakage of dangerous concentrations of propane into the air. At least if this is indoor air.

It seems to be known as F-gas known or CE 517/2014 and its effect in europe right now is about phasing out the most harmful fluorine based gas, (going from R-410A to R-32) and mandating regular maintenance and forbidding installation of heat pumps by non qualified individuals (to prevent leaks)

Many alternative refrigerants are combustible. That's not a big problem for stationary use, but in vehicles it is.

It is confusing that the article mentions buildings and not vehicles though.

I think R-410 just got sunsetted in the USA. It wont take effect for sometime and like other disused refrigerants technicians can reclaim the banned refrigerant from a system and use it somewhere else. The ban is on new equipment and new refrigerant production.

Fwiw, ElKaWe would be written as LKW which is shorthand for Lastkraftwagen (truck, lorry)

Natural refrigerant https://en.wikipedia.org/wiki/Natural_refrigerant :

> Natural refrigerants are considered substances that serve as refrigerants in refrigeration systems (including refrigerators, HVAC, and air conditioning). They are alternatives to synthetic refrigerants such as chlorofluorocarbon (CFC), hydrochlorofluorocarbon (HCFC), and hydrofluorocarbon (HFC) based refrigerants. Unlike other refrigerants, natural refrigerants can be found in nature and are commercially available thanks to physical industrial processes like fractional distillation, chemical reactions such as Haber process and spin-off gases. The most prominent of these include various natural hydrocarbons, carbon dioxide, ammonia, and water.[1] Natural refrigerants are preferred actually in new equipment to their synthetic counterparts for their presumption of higher degrees of sustainability. With the current technologies available, almost 75 percent of the refrigeration and air conditioning sector has the potential to be converted to natural refrigerants

Edit

Heat pump and refrigeration cycle > Thermodynamic cycles: https://en.wikipedia.org/wiki/Heat_pump_and_refrigeration_cy... :

> According to the second law of thermodynamics, heat cannot spontaneously flow from a colder location to a hotter area; work is required to achieve this.[3] An air conditioner requires work to cool a living space, moving heat from the interior being cooled (the heat source) to the outdoors (the heat sink). Similarly, a refrigerator moves heat from inside the cold icebox (the heat source) to the warmer room-temperature air of the kitchen (the heat sink). The operating principle of an ideal heat engine was described mathematically using the Carnot cycle by Sadi Carnot in 1824. An ideal refrigerator or heat pump can be thought of as an ideal heat engine that is operating in a reverse Carnot cycle.[4]

> Heat pump cycles and refrigeration cycles can be classified as vapor compression, vapor absorption, gas cycle, or Stirling cycle types.

Heat pump: https://en.wikipedia.org/wiki/Heat_pump :

> [...] When in heating mode, a refrigerant at the warmer temperature is compressed, becoming hot. Its thermal energy can be transferred to the cooler space. After being returned to the warmer space the refrigerant is decompressed — evaporated. It has delivered some of its thermal energy, so returns colder than the environment, and can again take up energy from the air or the ground in the warm space, and repeat the cycle.

> Air source heat pumps are the most common models, while other types include ground source heat pumps, water source heat pumps and exhaust air heat pumps. Large-scale heat pumps are also used in district heating systems.[2]

> The efficiency of a heat pump is expressed as a coefficient of performance (COP), or seasonal coefficient of performance (SCOP). The higher the number, the more efficient a heat pump is. When used for space heating, heat pumps are typically much more energy-efficient than electric resistance and other heaters. Because of their high efficiency and the increasing share of fossil-free sources in electrical grids, heat pumps can play a key role in climate change mitigation.[3][4] Consuming 1 kWh of electricity, they can transfer 3 to 6 kWh of thermal energy into a building.[5] The carbon footprint of heat pumps depends on how electricity is generated, but they usually reduce emissions in mild climates.[6] Heat pumps could satisfy over 80% of global space and water heating needs with a lower carbon footprint than gas-fired condensing boilers: however, in 2021 they only met 10%.[7]

>> [...] When in heating mode, a refrigerant at the warmer temperature is compressed, becoming hot. Its thermal energy can be transferred to the cooler space. After being returned to the warmer space the refrigerant is decompressed — evaporated. It has delivered some of its thermal energy, so returns colder than the environment, and can again take up energy from the air or the ground in the warm space, and repeat the cycle.

Great to see that even Wikipedia struggles with this :-)

This is 100% wrong.

Transferring heat from a warm space to a cold space happens on its own and does not need a heat pump. In the contrary, you can even extract mechanical work from this process.

Heating mode means heating a warm space by transferring heat from a colder space, which requires work.

If you convert all of the local thermal gradient to electricity, there's no work left to do without a pressure gradient in the loop or passive exchange to keep a thermal gradient there?

According to Superfluid Quantum Gravity, black holes and the quantum foam have a gravitational pressure gradient; vortices given density.

What efficiencies are people demonstrating with this effect?

Greater than running a pump and using the expansion and contraction of gases, as there you’re doing work to reach thermal via mechanical energy, rather than in this, where you are directly going from electrical to thermal. It’s inherently more efficient.

Is it? But even if it can't out-COP conventional heat pumps, perhaps it can significantly improve on mechanical complexity. Then it would make latent heat capture accessible to use cases where heat pumps will never be economically deployed. Imagine those materials used in a wheel-based counterflow heat exchanger: the complexity added to that already existing product would be very low, the utility would increase a lot.

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