> A comment on the YouTube video below complained, “Not a word about return on investment in the presentation. That means it’ll never pay off” MAGAlomaniacs are everywhere these days.
Given the supposed 50+ year lifespan of such a battery, I find it hard to believe it doesn't turn a profit at some point. And I understand that debunking low-effort accusations is asymmetric warfare. But why cite a random YouTube comment if you have no intention of addressing its claims? A more charitable interpretation is that it's meant to ragebait the readers. But to me, it seems like trying to make people feel ashamed for having doubts, by making a public example of a skeptic.
kragen · 19m ago
If, say, further insulating your house or building a sand battery will pay for itself in 50 years, it's a bad investment, financially speaking, and probably environmentally speaking as well. You can deploy "the same amount" of resources in something else with a higher ROI, like maybe solar panels with a one-year payback, and get a much bigger benefit. This is an important consideration as long as you are constrained by some kind of resource limitation.
So I think ROI is a first-order consideration.
skrebbel · 15m ago
Does anyone understand why people do this? I mean, really why? It's similar to eg climate protestors quoting all kinds of outrageously incorrect statistics as fact, or saying that $TECH can supply "4% of all households" with electricity, fully knowing that households only consume a tiny % of total energy, and so on.
I simply don't get it! The political landscape across the west is that there's swaths of people who've simply stopped believing mainstream media when they're reporting things, and somehow our reaction is to just lie even more? Try to out-lie camp Trump? I mean I don't think it's even possible to lie more than Trump so wouldn't the honest, nuanced truth be a a much better antidote than global left's current strategy of "also lie, but a bit less"?
I simply don't understand where it comes from. Like in what bizarro world is this shit a smart strategy? Is it all just incompetence?
csomar · 38m ago
The battery (am assuming it's just sand and metal) should be very cheap compared to Lithium especially in the places where you generated solar energy (they are hot and have a lot of sand).
The problem is: is it profitable to even store energy there? There is no mention beyond "In operation, the sand battery has demonstrated a round trip efficiency of 90 percent.". That doesn't mean much if you do not compare it to Lithium and you don't give me a breakdown of the costs.
The other thing: Size. Is that big thing enough to store energy for a city? a neighborhood? A building? A house?
If it's enough just for a house, then I have trouble seeing this scale.
kragen · 17m ago
1 MW is enough to heat somewhere between 100 and 2000 houses, depending on other factors like insulation, climate, and house size.
Sharlin · 24m ago
It's right in the title. 1 MW/100 MWh.
lupusreal · 1h ago
> And I understand that debunking low-effort accusations is asymmetric warfare
Is the comment even that unfair? Asserting that it will never pay off because the presentation avoided mentioning anything about the payoff might be a little bit cynical, but not terribly so. It could be fairly presumed that if the project is a clear economic win, they would be proudly bragging about it; and the opposite presumption is also reasonably fair, even if it turns out to be wrong.
And what does such cynicism have to do with "MAGA"? That asserted association seems much worse than the initial cynical assertion.
blueflow · 32m ago
> And what does such cynicism have to do with "MAGA"?
"Everyone i don't like is Hitler". It's a rather immature way of disagreeing.
Being concerned about economic viability is right-wing-coded in 2025, like eating healthy, having children, working out and spending time in nature. Explains why Europe is doing so poorly economically and is still paying Russia more for gas than they are giving in aid to Ukraine.
pastage · 38m ago
All those subjects in the right context are things the left wing fights for. Reducing a complex subject and then saying because you do not agree with my interpretation you are against children, is not optimal. E.g. Climate Activists are a pretty diverse group you will find lots of people who have said the same thing. It is obvious this is a PR/Research stunt, but it might still pay off. This is not a straight forward discussion where all people in the right or left groups has to agree.
flanked-evergl · 7m ago
I'm not saying it should be right wing coded, it's terrible that it is, but it has become so as far as I can tell.
ta1243 · 1h ago
People nowadays expect 10% return on their investment, so if you invest 1m you need to make 100k a year from it (120k to cover the deprecation over 50 years)
If you made 30k a year for 50 years you'd return 1.5m from your 1m investment, but you're only making 3%, which is a low return especially given the future risk (you'd have to run for 33 years just to get your initial investment back)
Either way it's worthwhile, because the reason people expect 10% is because the externalities are borne by others. Majority of people and countries in the world do not deem ROI to be the sole or even primary driver for investment, and judging investments only on the immediate financial reward already biases the conversation
kragen · 12m ago
> Majority of people and countries in the world do not deem ROI to be the sole or even primary driver for investment
I think this is a little unfair. If it were true, it would be the reason for wealth inequality: you're saying that the majority of people and countries are so financially irresponsible that they consume any resources they get without investing any. But in fact everyone I have observed closely, in every socioeconomic group, tries to optimize ROI. Most of them aren't very good at it, but they do try.
On the other hand, people who expect a 10% risk-free return are just going to get scammed. There are 10% opportunities in most people's lives—weatherstripping, coupon clipping, bulk food buying, etc.—but you can run out pretty quickly.
Avamander · 1h ago
> Majority of people and countries in the world do not deem ROI to be the sole or even primary driver for investment
It's partially that, other part is that we aren't really pricing in all the externalities of everything out there. So it's not that "there's no ROI", it's that "we aren't factoring things in the ROI calculation".
So while a heat battery might not make a huge profit, the ability to burn less fuel (less air pollution, less waste, etc), to offer redundancy and stability, the know-how and work it creates, that is all valuable as well.
testdelacc1 · 1h ago
I really like this comment. Concisely explains the points of view on an investment like this. There’s not much more to add.
This is why I open the comments before the link.
flanked-evergl · 1h ago
Resources are finite, if we blow it all on building sand batteries, then civilization collapses. Civilization can't run on virtue signalling alone, and what comes after western civilization collapses is, in fact, not the noble savages, it is rather ignoble savages — like the people that lynched Farkhunda Malikzada. She was brutally beaten with stones and sticks, dragged on the ground, thrown from a roof, run over with a car, and burned to death after being falsely accused. I understand many people prefer this over civilization, but I don't, and it's not noble.
kitd · 4h ago
I like these technologies. They may not be as energy efficient as using more exotic materials, but what they do use is simple, cheap and often sourced locally. Such economic factors are often as important to the ROI as the purely scientific ones.
pilif · 3h ago
> They may not be as energy efficient as using more exotic materials
yes and given that the energy you put in is practically free, it doesn't matter if it's not as efficient.
looofooo0 · 2h ago
I think with enough renewable in the grid, there will always be times when the costs are 0 or negative, so you can help stabilize the grid by consuming.
yurishimo · 1h ago
Are there downsides to "just" sending all of the extra energy to ground? I've often wondered why overpowering the grid has been talked about as this huge unsolvable problem.
I understand it's wasteful, of course, but waste in a ecosystem of vast abundance seems like a feature, not a bug.
ZeroGravitas · 1h ago
Solar and wind can be trivially turned down when not required. They are much, much better at it than traditional sources.
So easy that one of the actual problems we face is that by default grids will generally prefer to turn off the clean renewables and let the difficult to modulate fossil fuels run.
This is why negative prices are a good thing, financially incentivizing fossil producers to plan for flexibility and fining them when they fail to do so.
grues-dinner · 34m ago
> but waste in a ecosystem of vast abundance seems like a feature, not a bug.
The problem is that it's not a ecosystem of vast abundance, just occasional abundance. Literally no-one in the world right now is sitting on a constant supply of TWs of excess electrical power and saying "golly gee what are we going to do with all this". Perhaps France got closest in history and their prices still aren't "too cheap to meter".
You can "waste" the power (either by actually "burning" it to heat and dumping it, or just disconnecting the solar panels), but then you'll be short of power later and need to fall back on something expensive or with high externalities. It's also bad in terms of the capex for the solar panels (assuming solar), as you can't use your expensive plant as much as you want. If you can you'd rather use $10 of energy to store and sell it later, even as heat, at any price than just lose it all.
Even if you massively, massively overbuilt solar and wind so that you were in a "vast abundance" scenario on average, you still have to store some of it for night and/or winter.
lupusreal · 1h ago
As I understand it, you need to limit the current flow to ground to not create a fault that burns out the whole setup. The most practical way to do that is with a bank of resistors. At that point, the resistors are doing the work and you're just using the ground as a return path, which isn't necessary.
kragen · 26m ago
To clarify, the current flow never goes to ground; it goes back to where it started, which is why we call it a "circuit". When you do it without routing it through a load like a bank of resistors, it's called a "short circuit". Electromechanical generators will generally tend to catch on fire if you short-circuit them.
Solar panels have no problem with being short circuited; the amount of heat they produce in that state is the same as any other black object in sunlight.
Windmills are like any other electromechanical generator in this sense. You have to stop them with a brake. But that is totally a thing you can do, and quickly, and every mainstream windmill does it regularly (if only to handle overspeed winds safely), although, when this system fails, you get spectacular viral video content.
In the usual case where it works, though, you don't need a load bank either.
Load banks come into play when conventional inflexible baseload generators can't ramp down fast enough or when perverse market incentives pay renewables operators to pump power into the grid when it's not being demanded.
You'd think water would be easier to exchange heat with since it can slosh around the heat exchanger elements in the tank more easily. Which should translate to lower costs since you don't need as many exchanger structures in the medium.
Any guesses for the motivation in using sand? Maybe it's that you can heat it over 100C? But then big heat differences to the environment mean high conductive/radiation losses or heavier insulation requirements.
grues-dinner · 3h ago
Sand also mostly stays where you put it. While obviously water can be put in tanks easily enough, there's still more maintenance and inspection required and a gigantic watertight tank that will last n decades is substantially more expensive then a steel sand box. Plus it only goes to 100C unless you pressurise it and that really gets hard. Unplanned release of that much water at 100C is also extremely dangerous. Whereas even 500C sand will mostly just sit there. Plus the usual corrosion and scaling effects water systems love to develop at high temperatures.
Insulation isn't such an issue with sand because sand itself is fairly good insulator and obviously doesn't convect. 1m of sand is about the same as 10cm of air. 500C through 1m of sand if roughly 125W/m². Which isn't nothing but it's also 7m from the center to the edge, and the efficiencies only improve the bigger you make the silo.
Presumably they have a double-skin gap and other external insulation too. As the Icelandic hot water pipe systems show, which drop only a few degrees C over hundreds of kilometres of pipe (and thus a gigantic surface area to volume ratio), you can have really quite good insulation if you have space to make it thick.
The hassle of handling hot water is also presumably why they use hot air rather than water as a working fluid for heating the sand in the first place. The worst case if you spring a leak in a heat-transfer tube inside the tank is that a bit of air escapes. Leaking super-heated high-pressure water or steam into the (unpressurised) tank would be a much larger problem, and unloading up to 2000 tonnes of hot, damp, sand to plug it would be operationally very annoying if nothing else.
tarvaina · 4h ago
The Wikipedia article says:
"Rock, sand and concrete has a heat capacity about one third of water's. On the other hand, concrete can be heated to much higher temperatures (1200 °C) by for example electrical heating and therefore has a much higher overall volumetric capacity."
and
"Polar Night Energy installed a thermal battery in Finland that stores heat in a mass of sand. It was expected to reduce carbon emissions from the local heating network by as much as 70%. It is about 42 ft (13 m) tall and 50 ft (15 m) wide. It can store 100 MWh, with a round trip efficiency of 90%. Temperatures reach 1,112 ºF (600 ºC). The heat transfer medium is air, which can reach temperatures of 752 ºF (400 ºC) – can produce steam for industrial processes, or it can supply district heating using a heat exchanger."
internet_points · 3h ago
I learnt some new concepts here, specific heat capacity vs overall volumetric, things I kind of understood intuitively, but now much clearer:
If I add some fixed amount heat to some fixed volume of water, it might rise by 1℃, while the same volume of concrete rises by 3℃. And by the same logic, on release, that fixed volume of water dropping by 1℃ releases 3x as much heat as when that fixed volume of concrete drops by 1℃.
So if you can max heat water to 100℃, and max heat concrete to 1200℃, and on release you let it go to 10℃ (probably the range is less in practice), then the water can drop 90℃ and the concrete 1190℃, so even if the water releases 3x the amount of heat per ℃, the water just releases 270 (per volume) while the concrete releases 1190 (per volume)
privatelypublic · 2h ago
Also to add some practicals: you can drive a steam turbine with the concrete temps, but not with the water.
Also, looking at how hot water could theoretically get (decomposes between 2200-3300C), it looks like 1200C is an interesting limit. Above that and you get safety(practical) and cost issues with every material I could find (common salts, pure elements).
Sand just makes sense! Though, don't ever youtube sand battery.
stavros · 2h ago
Why not YouTube sand battery? I did it, and nothing much happened.
privatelypublic · 1h ago
Previously it was a bunch of overunity nutjobs.
stavros · 1h ago
Ahh right, I did see some preppers there, to be fair.
internet_points · 2h ago
> don't ever youtube sand battery
Huh? I just get stuff related to this article?
fulafel · 4h ago
The higher temperature output is a good point, you can't get 400C output for industrial processes from a 100C water based heat battery.
dinkblam · 1h ago
a Blast furnace needs closer to 2000° than 400°
in any case, how would you transport high temperatures to the industrial sites? water boils at 100° and few liquids boil above 400°. most liquids will be impractical due to cost or safety (combustibility, toxicity…).
Tuna-Fish · 2h ago
> But then big heat differences to the environment mean high conductive/radiation losses or heavier insulation requirements.
Square cube scaling means that insulation becomes trivial in total costs as you scale the installation up. Something that's convenient for a single household would probably be too hard to insulate, but this thing holds 2000t of sand.
Ekaros · 3h ago
District heating tends to operate at 50-70C at lowest. But more often up to 115C and in some case even 180C.
Even the lower range doesn't leave much delta in best case of boiling water. So you would need some type of heat pumps instead much simpler heat exchangers. So that is also one cost optimization.
decimalenough · 4h ago
The article mentions that they heat the sand to 500°C, which is not possible with water (well, at least not without turning into steam along the way).
Cthulhu_ · 3h ago
To be pedantic, yes you can but you'd need to pressurize it to uuhh... According to this calculator [0], you can get water to 370 degrees C if the pressure is 207 atmospheres, which is about the pressure of the ocean two kilometers deep.
Interestingly that's also about the pressure of gas in scuba tanks. Can't imagine how much energy to pressurize water to that
trhway · 2h ago
Due to incompressibility of liquids, pressurizing a liquid is very cheap energy-wise - orders of magnitude cheaper than pressurizing a gas. The issue is that pressurized liquid also requires correspondingly strong and expensive vessels and pipes.
sfn42 · 1h ago
You don't need to pressurize it. You just put it in a tank and apply heat, the water evaporates and creates pressure. Like a pressure cooker.
nick49488171 · 3h ago
How many kiloton of TNT equivalent?
grues-dinner · 2h ago
Well, if you say the energy stored is the 100MWh from the headline figure, and say you can arrange release every joule of all at once by flashing high-pressure water to steam at 1 atm that's about 0.1kT.
For this specific use case, you need to heat to far above the boiling point of water to retain some thermal efficiency. Sand/rock is better suited for storing the thermal energy at ~500 celcius.
vintermann · 3h ago
I wonder if there are any chemical effects from heating the sand to 500 degrees Celsius. Finely roasted sand.
isoprophlex · 3h ago
None, really. Pure, fine sand being mostly silicon dioxide, it melts at ~2000 and boils at ~3000 C, still without decomposing or reacting. It is really extremely chemically stable.
That said in practice, at scale... before filling up your storage tank you'd probably need to pre-heat it once to remove all moisture and volatile gunk adsorbed onto the sand.
If it were pure silica sand, you could presumably get even hotter before anything changes chemically, but at the that point you start having materials issues with metal parts of the system: 500C is about the limit for ordinary steels to lose strength (and many are less than that - heat effects can often start at 300C).
isoprophlex · 2h ago
Interesting, thanks for pointing that out, I didnt catch that they're not using actual sand.
LtdJorge · 3h ago
It's as inert as it gets
chii · 4h ago
perhaps sand is easier to heat to higher temps, and also it's less thermally conductive, so you'd lose less heat in storage for the same sized container.
d--b · 3h ago
They probably use the trick where they blow air in the sand to give it "liquid" properties where they need the sand to flow.
Helsinki has advanced integrated district heating and cooling. Over 300 MW of heat pumps by 2025.
Collecting heat from wast water is free energy. When you defecate, wash clothes or dishes, or take shower there is warm water and solids going down the pipes. That heat can be used. In the summer stored cold sea water can provide district cooling.
anttisalmela · 2h ago
Several cities in Finland have water based thermal batteries already, connected to local district heating networks. They have been previously used to store energy from existing combined heat and power plants, but now that wind power build up has created a lot of excess cheap power period, have been modified to include electric boilers.
Really interested in seeing how it fares in reality, almost sounds too good to be true.
jnsaff2 · 2h ago
Why too good to be true?
There are significant trade-offs with this technology.
It's storing heat, so if you need electricity then you eat a lot of efficiency. I think Vernon said ~45% round trip efficiency. Batteries are 90%+.
The storage is at a high temperature (500-600C) which means that you can't use heat-pumps to produce the heat to be stored. This means that you miss out on ~400% energy gains possible from converting electricity to heat.
So the efficiency is pretty low.
That said, solar PV is really cheap and moving large amounts of earth into a pile is also a very much solved problem so in some cases, notably higher latitudes which have very long days and low heat/electricity demand in the summer and the opposite in the winter, it could still be a very good solution.
Sharlin · 11m ago
The whole point is that the thermal energy is used directly, via district heating. These are not meant to store energy for electricity production (though they could do that if really needed – emergency power for various facilities? Maybe not worth it compared to diesel.)
Heat from existing thermal power plants can be stored directly and later distributed with no conversion loss; excess electricity from renewables can be turned to heat at 100% efficiency, but the problem is that peak heat demand and peak electricity supply do not typically coincide. Heat batteries are meant to solve that problem.
HPsquared · 2h ago
Yeah the efficiency is much less than 40% if you compare to heat pumps. It'll be something like 15% compared to those.
phtrivier · 1h ago
It seems to depend on having a network to distribute heat, which is something that you have to take into account... basically when you create your town ?
Or is there a way to "retrofit" district heating into houses with their own gas boiler or heat pump ?
Ekaros · 2m ago
Finland traditionally mostly used oil. If you have traditional water circulating radiators or underfloor water circuits it is pretty easy retrofit, just need to swap boiler with heat exchanger. Still, in many cases cost of infra is pretty high so heat pumps are often better options.
jpalomaki · 1h ago
Over half of Finland’s population lives in buildings connected to district heating.
lupusreal · 1h ago
They already have district heating.
davedx · 1h ago
Good idea but why is it being measured in MW/MWh when it’s not an electrical battery? I know they can be converted but maybe it should be measured in actual thermal units like Btu?
flowerthoughts · 12s ago
W and J are the SI units for power and energy. Those units make the most sense to use in Europe, regardless of the type of energy.
Wh is an abomination that has come about because professionals think consumer brains would expose if they ever saw the unit watt-seconds (J). No consumer had any preconceived notion of either Wh or J, so had we used J from the start, it wouldn't have been a problem...
(Yes, same with Ah vs C, though the battery pros also shot themselves in the foot by starting to use C (electrical charge) to mean "the capacity of this battery" when talking about charge rate, a.k.a. current.)
grues-dinner · 49m ago
Finland probably doesn't use US customary units like BTU (British Thermal Unit).
In fact even Britain doesn't often use such units - even gas boilers, heat pumps and some AC are specced in kW. You do see BTU (the /hr is often missing) sometimes on AC marketing. My theory is 18000 sounds big and impressive and 5.2kW sounds "meh". We definitely don't talk about "tons", and we buy gas in cubic metres or "units" (which is just kWh)
pintxo · 3h ago
Really like the idea, but my house alone has roughly 16 MWh/a heat consumption. Of which half gets consumed November through January.
So this system could supply 12 houses? Shows the importance of proper insulation, which is still on our todo list.
diggan · 2h ago
Sweden seems to have some of the highest "Electricity consumption per dwelling" (https://www.odyssee-mure.eu/publications/efficiency-by-secto...) in Europe, and sits at 10 MWh, which makes sense, it's a very cold country but with very well isolated houses in general :)
It sounds to me like you're likely an outlier here, for curiosities sake, where do you live?
pintxo · 1h ago
Germany, and these are numbers from our gas heater. But the house is almost 50 years old and not insulated to current standards (yet).
We got a heatpump this year, going to be interesting to see how this changes things.
lysace · 2h ago
16 MWh of electricity/year isn’t really an outlier for an electrically heated (via efficient heat pumps) house in Sweden either.
Your number above probably includes apartments and houses heated using district heating, e.g. from incinerating forest industry waste products.
Interestingly this looks like the same principle as a rocket mass heater or masonry heater, but on a larger scale and powered by renewable energy. They say the system can retain heat for weeks whereas the smaller thermal battery in a masonry heater is exhausted in a matter of hours. I wonder if this is a function of size or if the tank is heavily insulated? It would be interesting if this same system could work at smaller scales for off-grid heating by harnessing excess solar capacity. There’s a lot of waste involved in going from solar to battery vs directly to thermal energy, as long as it doesn’t bleed off before you need to use it.
Cthulhu_ · 3h ago
So why a surface sand silo instead of going down and using the soil/clay/bedrock/whatever is there? Ease of installation and maintenance?
whimsicalism · 3h ago
presumably you need the insulation from the air, otherwise it would just sort of dissipate through the ground
IshKebab · 2h ago
Open air is not a good insulator; that's why we wear coats! In contrast the ground is actually a pretty good insulator - that's why the London underground is so hot; the heat is all stuck in the ground.
It'll just be cheaper to build it on the ground than to dig a big hole and then build it in the hole.
crote · 1h ago
Rather the opposite, actually.
Air is a pretty good insulator, we wear coats to prevent air from moving around. How do most coats keep you warm? Trapped air.
The London underground is hot because the ground is an okay-ish heat conductor: it carries heat away well enough that for a century it essentially acted as an unlimited heat sink, so during its initial construction they never bothered to build proper ventilation. In fact, it was advertised as the perfect place to stay cool during the summer! But this has gone on for long enough that a significant area around the tubes has gradually warmed up from 14C to 19C-26C, and the smaller temperature gradient from tube-to-ground means less heat is carried away, which means the tubes now stay hotter.
Had ground been a great insulator the Victorians would've had to install a proper ventilation system from the start, and they wouldn't been having this issue right now. On the other hand, had ground been a great conductor this issue would've taken far longer to pop up as the heat would've spread through the ground faster.
whimsicalism · 1h ago
i don’t really know what to say, i wasn’t suggesting that the ground is very conductive of heat - but it is certainly much more conductive than the air is. just search.
the reason we wear coats has more to do with convection than the heat conduction of air
Findecanor · 2h ago
I'm not a building engineer, but my impression is that it does not matter as much as we might think.
A housing complex near mine got a massive tank like this installed thirty years ago, and I think they put it underground to be able to build a house on top.
jonespen · 4h ago
So, a gigantic sauna heater? Very on brand Tommi and Markku!
bjoli · 2h ago
90% roundtrip efficiency is pretty darn cool. I am not an engineer, but is it the high temperature difference that makes that possible?
IshKebab · 2h ago
I think they're talking about thermal efficiency (since this is a thermal battery, not an electrical battery). 90% of the heat they put in, they get out again. Probably all you need is good insulation.
smokel · 2h ago
That's only in heat transfer, that does not include generating electricity from it.
petesergeant · 4h ago
I live in a desert where we have district cooling (and no shortage of sand or solar power), instead of district heating. Wonder if they can pull off the same trick.
phh · 3h ago
Well you can't really do -600C sand (or anything), so the benefits of sand VS water largely diminished. "just" freezing water already gives you around 300C equivalent of sand (if my napkin is correct).
Also the point of this plant is to exploit the counter-correlation of cheap electricity and cold. Usually there is a bigger correlation between cheap electricity and heat.
Gravityloss · 2h ago
You can use heat to create cool by using absorption materials. It's of course way more complicated than with heat. But anyway with that, stored heat in sand could be used to create district cooling.
dzhiurgis · 3h ago
> you can't really do -600C sand (or anything)
You can if you stagger AC/HP or even peltier elements.
myrmidon · 2h ago
You misunderstood-- temperature is physically limited to -273°C, this is not an engineering problem. You have a smaller usable temperature range in a "cold storage" than with heat from fundamental physics alone.
pintxo · 3h ago
Cooling needs tend to correlate with the availability of solar energy. While heating especially far north does not so much.
Cthulhu_ · 3h ago
In theory, yeah, cooling the sand would work, and it wouldn't freeze / expand. You'd need to use a coolant that doesn't freeze though, and of course keep any liquid out of it.
dzhiurgis · 3h ago
Wonder if one could use staggered heatpumps here - in summer there's quite a bit of heat out there (some of which needs to be removed) so you could get 3-6x more bang for your buck.
grues-dinner · 1h ago
Staggering heatpumps doesn't help except on a practical level, like how climbing a staircase in big or small steps is the same. The only thing that matters to overall efficiency limits is the temperature delta.
The coefficient of performance for a heat pump from with cold/hot of 10C/40C is about 10 - this is ballpark where a domestic heating heat pump sits - this is why a heat pump house needs to be well-insulated to work - the heating loop isn't actually hot-hot like with a boiler). From 10C to 500C, it's 1.5. That's 9/0.5 = 18 times less advantage.
At any delta, you can eke out a bit of advantage as COP is always over one, but at some point overheads in the system start to overwhelm your theoretical advantage and you might as well keep it simple and use a cheap and reliable resistor to heat things for dead-cert COP of 1.
You could use a heat pump with a higher COP if you have a really gigantic tank that you only heat to about 40-50C, but obviously the thermal transfer from that is pretty bad and getting it where it needs to go while still being hot enough to be useful is a problem.
Havoc · 3h ago
Interesting capacity vs discharge ratio. Way slower than battery but presumably sand scales well
anovikov · 55m ago
Problem here is that if heating was done with electricity itself, it could have like 300% effective efficiency because of using heat pump, but a heat pump can't be used for 500C temperatures, it must be resistive heating. So even if no thermal loss occurs at all, we end up getting a lot, lot less heat than we could do otherwise. It's a lot better to use normal li-ion instead, surely 100 MWh means 500-ton battery and with longer life chemistries and thermal management, probably a 1000-ton one...
slumpvaldperson · 5h ago
Very interesting. Did anyone find a ROI calculation?
theshrike79 · 1h ago
It's a prototype, so not really relevant.
flanked-evergl · 1h ago
If they did, and it indicated that it's not just a money pit they would have shared it, so doubtful. As with most things in Europe it was likely done on the basis of a virtue signaling assessment alone. Europe's motto is going to keep saying "we have the resources" until it rapidly runs out of resources.
Norway's sovereign wealth fund will likely be completely gone in 20 years and will leave large swathes of the population without a pension because the Norwegian government works on the philosophy of "it's going to be okay, we have infinite money", already it's showing cracks as the only thing they actually have the money for is to make inflation skyrocket.
dguest · 1h ago
Finland is still 25% oil for electric generation [1] (and almost 40% fossil fuel). That means a lot of the electricity to heat the sand still comes from oil. It makes me wonder if this is more efficient than just using oil heating. Or some hybrid approach that uses oil to heat the sand.
Of course there are other benefits: it's still a good way to level electric generation, which is important for e.g. nuclear plants and wind power.
> Finland is still 25% oil for electric generation [1] (and almost 40% fossil fuel). That means a lot of the electricity to heat the sand still comes from oil.
This is not a valid conclusion. Battery projects like this are gonna charge/heat up when the electricity price is low, electricity price is low when supply/demand ratio is high and this often happens when renewable electricity is most available and makes up a disproportionate share of the electricity mix.
Edit: Your graph is not what you say it is, this shows primary energy (i.e. includes fuel/heating/...), not "electric generation". Electricity in Finland is mostly nuclear, wind, hydro and certainly not "40% fossil fuel".
nabla9 · 1h ago
95% of Finnish electricity is clean: nuclear, wind, hydro, renewable biomass. Oil 0.3%, coal 1.5%, net import of electricity 3.8% (most of it clean also).
Older private homes still use oil for heating. All new use electric, heat pumps, or geothermal heat pumps.
mzl · 33m ago
The point of these types of systems is that you can store energy when it is cheap to do so (there is an abundance of wind and/or solar energy) and use it later.
Hikikomori · 1h ago
Most of that is not for generating electricity as it includes transport and heat. Direct heating of homes traditionally used oil, wood and pellets, same as other Nordic countries. This is slowly being replaced with heat pumps that mainly use electricity from wind, water, nuclear or solar (not so much solar in Finland though).
> A comment on the YouTube video below complained, “Not a word about return on investment in the presentation. That means it’ll never pay off” MAGAlomaniacs are everywhere these days.
Given the supposed 50+ year lifespan of such a battery, I find it hard to believe it doesn't turn a profit at some point. And I understand that debunking low-effort accusations is asymmetric warfare. But why cite a random YouTube comment if you have no intention of addressing its claims? A more charitable interpretation is that it's meant to ragebait the readers. But to me, it seems like trying to make people feel ashamed for having doubts, by making a public example of a skeptic.
So I think ROI is a first-order consideration.
I simply don't get it! The political landscape across the west is that there's swaths of people who've simply stopped believing mainstream media when they're reporting things, and somehow our reaction is to just lie even more? Try to out-lie camp Trump? I mean I don't think it's even possible to lie more than Trump so wouldn't the honest, nuanced truth be a a much better antidote than global left's current strategy of "also lie, but a bit less"?
I simply don't understand where it comes from. Like in what bizarro world is this shit a smart strategy? Is it all just incompetence?
The problem is: is it profitable to even store energy there? There is no mention beyond "In operation, the sand battery has demonstrated a round trip efficiency of 90 percent.". That doesn't mean much if you do not compare it to Lithium and you don't give me a breakdown of the costs.
The other thing: Size. Is that big thing enough to store energy for a city? a neighborhood? A building? A house?
If it's enough just for a house, then I have trouble seeing this scale.
Is the comment even that unfair? Asserting that it will never pay off because the presentation avoided mentioning anything about the payoff might be a little bit cynical, but not terribly so. It could be fairly presumed that if the project is a clear economic win, they would be proudly bragging about it; and the opposite presumption is also reasonably fair, even if it turns out to be wrong.
And what does such cynicism have to do with "MAGA"? That asserted association seems much worse than the initial cynical assertion.
"Everyone i don't like is Hitler". It's a rather immature way of disagreeing.
There is a KYM page about this phenomenon: https://knowyourmeme.com/memes/everyone-i-dont-like-is-hitle...
If you made 30k a year for 50 years you'd return 1.5m from your 1m investment, but you're only making 3%, which is a low return especially given the future risk (you'd have to run for 33 years just to get your initial investment back)
Either way it's worthwhile, because the reason people expect 10% is because the externalities are borne by others. Majority of people and countries in the world do not deem ROI to be the sole or even primary driver for investment, and judging investments only on the immediate financial reward already biases the conversation
I think this is a little unfair. If it were true, it would be the reason for wealth inequality: you're saying that the majority of people and countries are so financially irresponsible that they consume any resources they get without investing any. But in fact everyone I have observed closely, in every socioeconomic group, tries to optimize ROI. Most of them aren't very good at it, but they do try.
On the other hand, people who expect a 10% risk-free return are just going to get scammed. There are 10% opportunities in most people's lives—weatherstripping, coupon clipping, bulk food buying, etc.—but you can run out pretty quickly.
It's partially that, other part is that we aren't really pricing in all the externalities of everything out there. So it's not that "there's no ROI", it's that "we aren't factoring things in the ROI calculation".
So while a heat battery might not make a huge profit, the ability to burn less fuel (less air pollution, less waste, etc), to offer redundancy and stability, the know-how and work it creates, that is all valuable as well.
This is why I open the comments before the link.
yes and given that the energy you put in is practically free, it doesn't matter if it's not as efficient.
I understand it's wasteful, of course, but waste in a ecosystem of vast abundance seems like a feature, not a bug.
So easy that one of the actual problems we face is that by default grids will generally prefer to turn off the clean renewables and let the difficult to modulate fossil fuels run.
This is why negative prices are a good thing, financially incentivizing fossil producers to plan for flexibility and fining them when they fail to do so.
The problem is that it's not a ecosystem of vast abundance, just occasional abundance. Literally no-one in the world right now is sitting on a constant supply of TWs of excess electrical power and saying "golly gee what are we going to do with all this". Perhaps France got closest in history and their prices still aren't "too cheap to meter".
You can "waste" the power (either by actually "burning" it to heat and dumping it, or just disconnecting the solar panels), but then you'll be short of power later and need to fall back on something expensive or with high externalities. It's also bad in terms of the capex for the solar panels (assuming solar), as you can't use your expensive plant as much as you want. If you can you'd rather use $10 of energy to store and sell it later, even as heat, at any price than just lose it all.
Even if you massively, massively overbuilt solar and wind so that you were in a "vast abundance" scenario on average, you still have to store some of it for night and/or winter.
Solar panels have no problem with being short circuited; the amount of heat they produce in that state is the same as any other black object in sunlight.
Windmills are like any other electromechanical generator in this sense. You have to stop them with a brake. But that is totally a thing you can do, and quickly, and every mainstream windmill does it regularly (if only to handle overspeed winds safely), although, when this system fails, you get spectacular viral video content.
In the usual case where it works, though, you don't need a load bank either.
Load banks come into play when conventional inflexible baseload generators can't ramp down fast enough or when perverse market incentives pay renewables operators to pump power into the grid when it's not being demanded.
You'd think water would be easier to exchange heat with since it can slosh around the heat exchanger elements in the tank more easily. Which should translate to lower costs since you don't need as many exchanger structures in the medium.
Any guesses for the motivation in using sand? Maybe it's that you can heat it over 100C? But then big heat differences to the environment mean high conductive/radiation losses or heavier insulation requirements.
Insulation isn't such an issue with sand because sand itself is fairly good insulator and obviously doesn't convect. 1m of sand is about the same as 10cm of air. 500C through 1m of sand if roughly 125W/m². Which isn't nothing but it's also 7m from the center to the edge, and the efficiencies only improve the bigger you make the silo.
Presumably they have a double-skin gap and other external insulation too. As the Icelandic hot water pipe systems show, which drop only a few degrees C over hundreds of kilometres of pipe (and thus a gigantic surface area to volume ratio), you can have really quite good insulation if you have space to make it thick.
The hassle of handling hot water is also presumably why they use hot air rather than water as a working fluid for heating the sand in the first place. The worst case if you spring a leak in a heat-transfer tube inside the tank is that a bit of air escapes. Leaking super-heated high-pressure water or steam into the (unpressurised) tank would be a much larger problem, and unloading up to 2000 tonnes of hot, damp, sand to plug it would be operationally very annoying if nothing else.
"Rock, sand and concrete has a heat capacity about one third of water's. On the other hand, concrete can be heated to much higher temperatures (1200 °C) by for example electrical heating and therefore has a much higher overall volumetric capacity."
and
"Polar Night Energy installed a thermal battery in Finland that stores heat in a mass of sand. It was expected to reduce carbon emissions from the local heating network by as much as 70%. It is about 42 ft (13 m) tall and 50 ft (15 m) wide. It can store 100 MWh, with a round trip efficiency of 90%. Temperatures reach 1,112 ºF (600 ºC). The heat transfer medium is air, which can reach temperatures of 752 ºF (400 ºC) – can produce steam for industrial processes, or it can supply district heating using a heat exchanger."
If I add some fixed amount heat to some fixed volume of water, it might rise by 1℃, while the same volume of concrete rises by 3℃. And by the same logic, on release, that fixed volume of water dropping by 1℃ releases 3x as much heat as when that fixed volume of concrete drops by 1℃.
So if you can max heat water to 100℃, and max heat concrete to 1200℃, and on release you let it go to 10℃ (probably the range is less in practice), then the water can drop 90℃ and the concrete 1190℃, so even if the water releases 3x the amount of heat per ℃, the water just releases 270 (per volume) while the concrete releases 1190 (per volume)
Also, looking at how hot water could theoretically get (decomposes between 2200-3300C), it looks like 1200C is an interesting limit. Above that and you get safety(practical) and cost issues with every material I could find (common salts, pure elements).
Sand just makes sense! Though, don't ever youtube sand battery.
Huh? I just get stuff related to this article?
in any case, how would you transport high temperatures to the industrial sites? water boils at 100° and few liquids boil above 400°. most liquids will be impractical due to cost or safety (combustibility, toxicity…).
Square cube scaling means that insulation becomes trivial in total costs as you scale the installation up. Something that's convenient for a single household would probably be too hard to insulate, but this thing holds 2000t of sand.
Even the lower range doesn't leave much delta in best case of boiling water. So you would need some type of heat pumps instead much simpler heat exchangers. So that is also one cost optimization.
[0] https://www.engineeringtoolbox.com/water-vapor-saturation-pr...
So quite a bang - allegedly this is 200lb, so about the same: https://www.youtube.com/watch?v=ZDgvar7ON54
That said in practice, at scale... before filling up your storage tank you'd probably need to pre-heat it once to remove all moisture and volatile gunk adsorbed onto the sand.
If it were pure silica sand, you could presumably get even hotter before anything changes chemically, but at the that point you start having materials issues with metal parts of the system: 500C is about the limit for ordinary steels to lose strength (and many are less than that - heat effects can often start at 300C).
For those who haven't seen it there is a famous Mark Rober video: https://www.youtube.com/watch?v=My4RA5I0FKs
Collecting heat from wast water is free energy. When you defecate, wash clothes or dishes, or take shower there is warm water and solids going down the pipes. That heat can be used. In the summer stored cold sea water can provide district cooling.
Really interested in seeing how it fares in reality, almost sounds too good to be true.
There are significant trade-offs with this technology.
It's storing heat, so if you need electricity then you eat a lot of efficiency. I think Vernon said ~45% round trip efficiency. Batteries are 90%+.
The storage is at a high temperature (500-600C) which means that you can't use heat-pumps to produce the heat to be stored. This means that you miss out on ~400% energy gains possible from converting electricity to heat.
So the efficiency is pretty low.
That said, solar PV is really cheap and moving large amounts of earth into a pile is also a very much solved problem so in some cases, notably higher latitudes which have very long days and low heat/electricity demand in the summer and the opposite in the winter, it could still be a very good solution.
Heat from existing thermal power plants can be stored directly and later distributed with no conversion loss; excess electricity from renewables can be turned to heat at 100% efficiency, but the problem is that peak heat demand and peak electricity supply do not typically coincide. Heat batteries are meant to solve that problem.
Or is there a way to "retrofit" district heating into houses with their own gas boiler or heat pump ?
Wh is an abomination that has come about because professionals think consumer brains would expose if they ever saw the unit watt-seconds (J). No consumer had any preconceived notion of either Wh or J, so had we used J from the start, it wouldn't have been a problem...
(Yes, same with Ah vs C, though the battery pros also shot themselves in the foot by starting to use C (electrical charge) to mean "the capacity of this battery" when talking about charge rate, a.k.a. current.)
In fact even Britain doesn't often use such units - even gas boilers, heat pumps and some AC are specced in kW. You do see BTU (the /hr is often missing) sometimes on AC marketing. My theory is 18000 sounds big and impressive and 5.2kW sounds "meh". We definitely don't talk about "tons", and we buy gas in cubic metres or "units" (which is just kWh)
So this system could supply 12 houses? Shows the importance of proper insulation, which is still on our todo list.
It sounds to me like you're likely an outlier here, for curiosities sake, where do you live?
We got a heatpump this year, going to be interesting to see how this changes things.
Your number above probably includes apartments and houses heated using district heating, e.g. from incinerating forest industry waste products.
It'll just be cheaper to build it on the ground than to dig a big hole and then build it in the hole.
Air is a pretty good insulator, we wear coats to prevent air from moving around. How do most coats keep you warm? Trapped air.
The London underground is hot because the ground is an okay-ish heat conductor: it carries heat away well enough that for a century it essentially acted as an unlimited heat sink, so during its initial construction they never bothered to build proper ventilation. In fact, it was advertised as the perfect place to stay cool during the summer! But this has gone on for long enough that a significant area around the tubes has gradually warmed up from 14C to 19C-26C, and the smaller temperature gradient from tube-to-ground means less heat is carried away, which means the tubes now stay hotter.
Had ground been a great insulator the Victorians would've had to install a proper ventilation system from the start, and they wouldn't been having this issue right now. On the other hand, had ground been a great conductor this issue would've taken far longer to pop up as the heat would've spread through the ground faster.
the reason we wear coats has more to do with convection than the heat conduction of air
A housing complex near mine got a massive tank like this installed thirty years ago, and I think they put it underground to be able to build a house on top.
Also the point of this plant is to exploit the counter-correlation of cheap electricity and cold. Usually there is a bigger correlation between cheap electricity and heat.
You can if you stagger AC/HP or even peltier elements.
The coefficient of performance for a heat pump from with cold/hot of 10C/40C is about 10 - this is ballpark where a domestic heating heat pump sits - this is why a heat pump house needs to be well-insulated to work - the heating loop isn't actually hot-hot like with a boiler). From 10C to 500C, it's 1.5. That's 9/0.5 = 18 times less advantage.
At any delta, you can eke out a bit of advantage as COP is always over one, but at some point overheads in the system start to overwhelm your theoretical advantage and you might as well keep it simple and use a cheap and reliable resistor to heat things for dead-cert COP of 1.
You could use a heat pump with a higher COP if you have a really gigantic tank that you only heat to about 40-50C, but obviously the thermal transfer from that is pretty bad and getting it where it needs to go while still being hot enough to be useful is a problem.
Norway's sovereign wealth fund will likely be completely gone in 20 years and will leave large swathes of the population without a pension because the Norwegian government works on the philosophy of "it's going to be okay, we have infinite money", already it's showing cracks as the only thing they actually have the money for is to make inflation skyrocket.
Of course there are other benefits: it's still a good way to level electric generation, which is important for e.g. nuclear plants and wind power.
[1]: https://ourworldindata.org/grapher/energy-consumption-by-sou...
This is not a valid conclusion. Battery projects like this are gonna charge/heat up when the electricity price is low, electricity price is low when supply/demand ratio is high and this often happens when renewable electricity is most available and makes up a disproportionate share of the electricity mix.
Edit: Your graph is not what you say it is, this shows primary energy (i.e. includes fuel/heating/...), not "electric generation". Electricity in Finland is mostly nuclear, wind, hydro and certainly not "40% fossil fuel".
Older private homes still use oil for heating. All new use electric, heat pumps, or geothermal heat pumps.