# New lossless heat preservation process developed(heat storage for years)

**URL:** <https://boards.straightdope.com/t/new-lossless-heat-preservation-process-developed-heat-storage-for-years/1022921>\
**Category:** Factual Questions\
**Created:** [September 10, 2025, 10:26pm UTC](https://boards.straightdope.com/t/new-lossless-heat-preservation-process-developed-heat-storage-for-years/1022921 "2025-09-10T22:26:45Z")\
**Posts on this page:** 12\
**Page:** 1

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**Author:** ![Al128](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/al128/32/16541_2.png) [@Al128](https://boards.straightdope.com/u/Al128)\
**Post date:** [September 10, 2025, 10:26pm UTC](https://boards.straightdope.com/t/new-lossless-heat-preservation-process-developed-heat-storage-for-years/1022921/1 "2025-09-10T22:26:45Z")

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ok sorry I had to abbreviate the title somewhat … its NEARLY lossless.

Were this on YT, I’d chalk it up to the perpetuum mobile /flatearthers crazy bunch… but

here is the news-article:

[https://science.orf.at/stories/3231641/](https://science.orf.at/stories/3231641/) \<\<== in german, but a google translate should help out

“Good news”: - both ORF (think: BBC of Austria) and TU-Wien (Vienna U of Technology) are normally pretty solid institutions.

here a couple of highlights from the article:

[snip]

_In its process, the TU Vienna team uses an azure salt hydrate (a salt in whose crystal structure water molecules are inserted) and a thermal oil as a carrier solution. If heat is supplied, the water splits off from the salt hydrate. In chemistry, this process is referred to as an „activated state“._

_„The activated substance can be stored very nicely and used as an energy source“, explains Winter. You can even transport it effortlessly from A to B, either in a piping system or in tanks._

…

_Conversely, if you add water back to the energy source, the heat is released again. „That’s the beauty of this technology“, says Winter: „The energy source is not lost, it is used again and again.“_

_…_

_The team was also able to show that the heat in the new reactor can be stored for longer periods of time with almost no loss. If stored well, the heat can be accessed again even after „years, up to decades“. „Technically there are no limits here“, says the process engineer._

here a bit more “meat’n’facts” I found in this paper (same guy): [Calcium chloride dihydrate as a promising system for seasonal heat storage in a suspension reactor - ScienceDirect](https://www.sciencedirect.com/science/article/pii/S1359431124022257?via%3Dihub)

## _Abstract_

… _This study investigates the reversible dehydration of calcium chloride dihydrate which has been recognised as a suitable thermochemical material in prior studies. A new method is introduced by investigating the reaction in a lab-scale batch-type suspension reactor. In the reactor, a mechanical stirrer suspends the solid thermochemical material in an inert liquid, to prevent agglomeration of the particles. The investigation involves a parameter variation that includes different suspension media, different mass fractions of the solid reactant, as well as different system pressures during charging. The experimental investigation renders 40 wt% solid or lower as the most promising mass fraction to avoid agglomeration. Vegetable oils show promising results as suspension media. However, they lack thermal stability in the temperature range of up to 210 °C. Mineral oil can ensure thermal and cycle stability. Furthermore, a notable reduction in the dehydration reaction temperatures (176 to 109 °C) is observed when the system pressure is decreased down to 50 mbar. The study concludes that calcium chloride dihydrate has the potential to be used for 22 stable charging and discharging cycles in a mineral oil suspension and that lowering the system pressure can reduce the required charging temperature of the system. To further enhance the suspension method, it is essential to focus on mass transfer and foam mitigation during the dehydration reaction._

I’d be interested in hearing your thoughts on this (to be honest, I [layman] have trouble computing this - but the academic behind this has a pretty solid background in this type of research.

So,

- will this work?
- how?

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**Author:** ![Sigene](https://avatars.discourse-cdn.com/v4/letter/s/df788c/32.png) [@Sigene](https://boards.straightdope.com/u/Sigene)\
**Post date:** [September 10, 2025, 10:59pm UTC](https://boards.straightdope.com/t/new-lossless-heat-preservation-process-developed-heat-storage-for-years/1022921/2 "2025-09-10T22:59:29Z")

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How does one define ‘lossless heat preservation’ vs. ‘lost’ heat? Heat seems to be the bottom of the energy ladder, any time you put heat in to heat something up, it will cool down eventually emitting that same amount of heat.

The loss is where the heat leaks out of the system through the pipes, tubes, wires. This process can still leak heat out that way too. I’m guessing not ‘every bit of heat’ that goes into the container splits off a water in the salt hydrate. The quantum efficiency of this is less then 100%.

I think the advantage is that you can store heat for a long time, though other systems can do this too, like sodium acetate.

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**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\
**Post date:** [September 10, 2025, 11:34pm UTC](https://boards.straightdope.com/t/new-lossless-heat-preservation-process-developed-heat-storage-for-years/1022921/3 "2025-09-10T23:34:22Z")

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It sounds like they’ve found a substance that goes through a state change with a very large latent heat. Latent heat is useful, because it doesn’t come with a temperature change. If the state transition temperature is close to room temperature, it’ll be easy to store it for a long time, without heat leaking out to the surroundings.

On the other hand, the transition temperature being close to room temperature would also mean that the heat can’t be used very efficiently when you do release it. It’d be fine for climate control in a building in a temperate climate, say, where some times of the year you want to cool it and other times of the year you want to heat it, so you can store summer heat to be used in winter. But it wouldn’t be useful for something like a solar thermal power plant.

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**Author:** ![Dr.Strangelove](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dr.strangelove/32/6613_2.png) [@Dr.Strangelove](https://boards.straightdope.com/u/Dr.Strangelove)\
**Post date:** [September 11, 2025, 12:05am UTC](https://boards.straightdope.com/t/new-lossless-heat-preservation-process-developed-heat-storage-for-years/1022921/4 "2025-09-11T00:05:36Z")

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210 C kinda sucks for heat storage.

I am much more interested in this project:

> **[Building Ultra Cheap Energy Storage for Solar PV](https://austinvernon.substack.com/p/building-ultra-cheap-energy-storage)**
>
> Solar still needs storage cheap enough to move energy between seasons. I have been working on a startup to do this for the last two years.

Basically, heat storage in dirt. It can handle temperatures of \>600 C, which makes conversion back to electricity much more efficient than lower temperatures.

The advantage of dirt is that it’s ludicrously cheap. You just pile it up. You need a network of heat transfer devices, which are the relatively expensive part, but that is probably a solvable problem.

The disadvantage, as it were, is that dirt has low thermal conductivity, so you can only store/extract heat at low rates. But this is actually not a problem, because the goal is for very long-term storage (months). If it takes months to recharge/discharge, that’s fine. You can use batteries to cover the day/night cycling if required. Batteries are cheap enough to cover energy needs for a day; it’s the several-month range that needs something cheaper. Hydroelectric works but only in limited locations. Piles of dirt work anywhere.

The key behind all of this is that solar PV is also exceptionally cheap in terms of generation. It’s the storage, conversion, and transmission that adds to the price. But if you put the dirt piles right next to the panels, much of this is avoided.

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**Author:** ![peccavi](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/peccavi/32/388_2.png) [@peccavi](https://boards.straightdope.com/u/peccavi)\
**Post date:** [September 11, 2025, 12:27am UTC](https://boards.straightdope.com/t/new-lossless-heat-preservation-process-developed-heat-storage-for-years/1022921/5 "2025-09-11T00:27:20Z")

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The full calcium chloride dihydrate paper is available at Science Direct

> **[Calcium chloride dihydrate as a promising system for seasonal heat storage in...](https://www.sciencedirect.com/science/article/pii/S1359431124022257)**
>
> The shift to renewable energy sources increases the demand for energy storage to balance supply and demand. The call for heat storage solutions is par…

The research isn’t world shattering. There is apparently a fair amount of research into materials and methods for _Thermochemical energy storage_ (TCES) and this article describes the state of research as Technology Readiness Level (TRL) 1-4 , with 4 defined as component and/or subsystem validation in a laboratory environment, for those unfamiliar with TRL. There’s a nice discussion of heat storage technologies early in the paper.

The material itself has been researched among others (there are copious references in the paper) and the highlights of the paper indicate progress, not breakthrough:

> Highlights
> 
> [Calcium chloride](https://www.sciencedirect.com/topics/chemical-engineering/calcium-chloride) is used for [TCES](https://www.sciencedirect.com/topics/engineering/thermochemical-storage) in a stirred tank using oil for the first time.
> 
> Solid weight fractions of 40 wt% and lower prevent agglomeration in the suspension.
> 
> [Rapeseed oil](https://www.sciencedirect.com/topics/engineering/rapeseed-oil) shows good cycle stability in 5 cycles despite [thermal degradation](https://www.sciencedirect.com/topics/engineering/thermal-degradation).
> 
> The dehydration-hydration cycle stability is proven for 22 runs in mineral oil.
> 
> Lowering psystem to 50 mbar decreases Tstart of the dehydration (175 °C to 109 °C).

So, interesting incremental advance with potential utility eventually, but not breakthrough versus other similar research. It sounds like the university’s PR folks go hold of the paper and ran with it.

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**Author:** ![md-2000](https://avatars.discourse-cdn.com/v4/letter/m/9d8465/32.png) [@md-2000](https://boards.straightdope.com/u/md-2000)\
**Post date:** [September 11, 2025, 4:29pm UTC](https://boards.straightdope.com/t/new-lossless-heat-preservation-process-developed-heat-storage-for-years/1022921/6 "2025-09-11T16:29:24Z")

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So basically it’s storing energy (not heat) as a form of chemical composition change. Sort of like (crude example) storing energy by using it to create oil or methane, and then burning it when heat is required. Except - a simpler chemical reaction to store a decent amount of energy, no need for any external input like oxygen for combustion (I gather the same water can be extracted and used again?) and the reaction is efficient and can go back and forth over and over without degradation?

The key to storing heat is of course insulation. The heat that escapes to the outside environment is lost. Something like a dirt pile (or underground) relies on building a surrounding layer of material that eventually has a temperature gradient and slow conduction so that less heat is lost as conduction to outside as the core is heated above the surroundings and cooled below (heat flows back) during useage cycles and much less is lost to the surroundings.

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**Author:** ![JacobSwan](https://avatars.discourse-cdn.com/v4/letter/j/a6a055/32.png) [@JacobSwan](https://boards.straightdope.com/u/JacobSwan)\
**Post date:** [September 12, 2025, 10:39am UTC](https://boards.straightdope.com/t/new-lossless-heat-preservation-process-developed-heat-storage-for-years/1022921/7 "2025-09-12T10:39:22Z")

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How is this different to those self heating meals used by campers for decades? They rely on slaked lime and water mixing to release the heat. Pretty much the same reaction as described here surely?

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**Author:** ![Maserschmidt](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/maserschmidt/32/18829_2.png) [@Maserschmidt](https://boards.straightdope.com/u/Maserschmidt)\
**Post date:** [September 12, 2025, 11:09am UTC](https://boards.straightdope.com/t/new-lossless-heat-preservation-process-developed-heat-storage-for-years/1022921/8 "2025-09-12T11:09:29Z")

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> [@Dr.Strangelove](#):
>
> The advantage of dirt is that it’s ludicrously cheap. You just pile it up. You need a network of heat transfer devices, which are the relatively expensive part, but that is probably a solvable problem.

I know sand storage is also an option, and it seems like it would be a more efficient - but is there a big difference in cost?

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**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\
**Post date:** [September 12, 2025, 11:15am UTC](https://boards.straightdope.com/t/new-lossless-heat-preservation-process-developed-heat-storage-for-years/1022921/9 "2025-09-12T11:15:20Z")

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The self-heating meals do not use a reversible chemical process. They’re one-way. Just like a fire.

The relevance of these newer ideas is more like a heat battery. It can be charged and discharged and recharged with little round-trip loss. And most significantly for something storing heat, it doesn’t have continuous leakage to the environment like an actual temperature delta would have. So like a battery that doesn’t self-discharge while just sitting on a shelf.

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**Author:** ![Napier](https://avatars.discourse-cdn.com/v4/letter/n/ce73a5/32.png) [@Napier](https://boards.straightdope.com/u/Napier)\
**Post date:** [September 12, 2025, 12:02pm UTC](https://boards.straightdope.com/t/new-lossless-heat-preservation-process-developed-heat-storage-for-years/1022921/10 "2025-09-12T12:02:14Z")

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From just a quick reading, I understand that this does not store thermal energy by having the substances stay hot. It’s transforming back and forth between thermal and chemical energy. Thermal losses through insulation aren’t an issue, at least not during the long times energy can be stored. It doesn’t sound revolutionary. It’s not an entirely new idea. It’s not a perpetual motion machine or a free energy machine. It does sound real, and perhaps pretty useful.

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**Author:** ![md-2000](https://avatars.discourse-cdn.com/v4/letter/m/9d8465/32.png) [@md-2000](https://boards.straightdope.com/u/md-2000)\
**Post date:** [September 13, 2025, 4:37am UTC](https://boards.straightdope.com/t/new-lossless-heat-preservation-process-developed-heat-storage-for-years/1022921/11 "2025-09-13T04:37:28Z")

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The real issue then is how easily (efficiently) the return heat from the reaction can be converted to the appropriate energy. If the goal is to heat a house, it’s really good. If you need electricity or motive power, less so.

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**Author:** ![dtilque](https://avatars.discourse-cdn.com/v4/letter/d/d6d6ee/32.png) [@dtilque](https://boards.straightdope.com/u/dtilque)\
**Post date:** [September 13, 2025, 5:27am UTC](https://boards.straightdope.com/t/new-lossless-heat-preservation-process-developed-heat-storage-for-years/1022921/12 "2025-09-13T05:27:11Z")

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> [@Maserschmidt](#):
>
> I know sand storage is also an option

> **[Finland warms up the world’s largest sand battery, and the economics look...](https://techcrunch.com/2025/06/16/finland-warms-up-the-worlds-largest-sand-battery-and-the-economics-look-appealing/)**
>
> Pornainen recently turned on a 100 MWh thermal battery filled with ground up soapstone.