Very interesting. Did anyone find a ROI calculation?
replies(2):
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.
"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."
Really interested in seeing how it fares in reality, almost sounds too good to be true.
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)
For those who haven't seen it there is a famous Mark Rober video: https://www.youtube.com/watch?v=My4RA5I0FKs
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.
[0] https://www.engineeringtoolbox.com/water-vapor-saturation-pr...
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.
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.
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.
So this system could supply 12 houses? Shows the importance of proper insulation, which is still on our todo list.
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.
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.
It sounds to me like you're likely an outlier here, for curiosities sake, where do you live?
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.
So quite a bang - allegedly this is 200lb, so about the same: https://www.youtube.com/watch?v=ZDgvar7ON54
Huh? I just get stuff related to this article?
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).
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.
Your number above probably includes apartments and houses heated using district heating, e.g. from incinerating forest industry waste products.
> 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.
It'll just be cheaper to build it on the ground than to dig a big hole and then build it in the hole.
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
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.
the reason we wear coats has more to do with convection than the heat conduction of air
I understand it's wasteful, of course, but waste in a ecosystem of vast abundance seems like a feature, not a bug.
This is why I open the comments before the link.
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...
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.
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.
Or is there a way to "retrofit" district heating into houses with their own gas boiler or heat pump ?
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".
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.
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.
Older private homes still use oil for heating. All new use electric, heat pumps, or geothermal heat pumps.
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…).
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.
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)
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.
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 that you can't sell 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.
"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...
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.
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?
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.
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.
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.
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.)
Surely the lifespan is almost forever. It's just a tank full of sand and some heating pipes. Maybe the pipes and/or control electronics needs to be replaced occasionally, but nothing should happen to the sand inside - like ever.
I think the more likely explanation is that this is a pilot project by a clean energy startup, it intentionally operates at a loss because it's RnD rather than mature tech, everyone involved is okay with this, and the company doesn't want to release its modelling of future ROI because that's valuable proprietary data and giving it away to clients and competitors is dumb.
Average S&P total return (reinvesting dividends) is well over 10% over any appreciable timeframe (say 30 years), even during really low times (say buying at the peaks in 1999 or 1972)
Then again, the same also goes for the other storage methods as the spread compresses. Eventually, as always, it all comes down to who can do it on the thinnest shoestring. 1/4 the cost, but the thermodynamic efficiency is 1/3 (direct heat vs batteries + heat pump, say) is still a winner. Finns aren't going to stop needing heat in winter soon, and if you can provide it even a fraction under the cost of battery electricity and a heat pump, you get the customer. And the district heat infrastructure probably already exists.
Plenty of leftists have their own reasons to distrust media. But scarcely anyone imagines reasons why someone else would lose trust. Not that they could do anything about it anyway.
The "global left" is not a real thing. I mean, of course you can draw lines around groups any way you like, but this one doesn't offer meaningful insight.
Eg that graph is not Finnish electricity usage. It's ALL energy, including cars and planes that still use oil...
Anyway, to explain my mistake, the data did not look "insane" to me, it's about right for most countries, and even if it had been correct for Finland the method they described might be favorable (some electric sources need leveling and using extra energy for heat is better than dumping it). Honest mistake, I'm not here with some agenda, and I learned of it by posting.
Anwyay, thanks for the correction! It's amazing (in a good way) that internet communicators can see something that looks plausible, but is wrong, and correct it! You've restored (some of) my faith in the internet.
https://ourworldindata.org/grapher/electricity-prod-source-s...
and it backs up your point. Sorry to any Fins I might have offended with my lazy post.
Theoretically this would be an endless cycle, which is of course constrained by very practical needs of the electricity users.
And in this context it's much more obvious that it can notionally deliver energy at a peak rate of about 1% capacity per hour. If you said 1MW/360GJ, I don't think that would be nearly as clear.
Same for batteries, which started with car batteries/deep cycle batteries, rather than AA batteries, which usual don't even say, and phones. A battery that provides 1 amp (at 12V, but that's already given in a system) for 50 hours. Makes immediate practical sense, especially when equipment is often labelled in current draw and you can measure amps with an ammeter. 2.16MJ far less so.
Something that stores _energy_ is a battery. Not necessarily electric energy. You can absolutely have a battery with mechanical energy (wound up springs), a battery with kinetic energy (a weight in a shaft) a battery with nuclear energy (Thermal reactor in a satellite), a battery with thermal energy (silo full of very hot sand) or a battery with chemical energy such as a Li-ion battery.
This stores 100 MWh heat energy, so it is a battery.
From wikipedia:
> Energy storage is the capture of energy produced at one time for use at a later time to reduce imbalances between energy demand and energy production. A device that stores energy is generally called an accumulator or battery.
Now, in practice you _probably_ don't want to do this, because, in this case, you have district heating demand, which is a far more efficient use of the power.
The sand is the least complex part. Industrial facilities like this take a lot to keep running.
Also it is a mess, as is traditional for US customary units:
> A Btu was originally defined as the amount of heat required to raise the temperature of one pound of liquid water by one degree Fahrenheit at a constant pressure of one atmospheric unit. There are several different definitions of the Btu that differ slightly.
(Best one is still the fluid oz, tho. A US customary fluid oz is about 29.6ml, a US food labelling fluid oz is exactly 30ml.)
And of course it's still a win if you can heat the return water half of the way to spec with the battery, it's not necessary to have the battery heat it all the way to the plant outgoing temp.
District heating systems have been happily using ~90C water based heat batteries for a long time.
Apparently now it's time for the world to return to populist authoritarianism and isolationist policy in order to bury our heads in the...sand...until we have to collectively rise against them again. Except, this time, it may be America who bears the brutal brunt.
In the end it comes to balance with cost, simplicity, capacity and such. Heat pumps do allow extracting heat from colder storage medium. But on other hand electric heating elements and heat exchangers are very much simpler and cheaper.
nobody cares about his car loosing value as soon as you drive off the parking lot. Or any other appliance - a fridge will never have a ROI, a washing machine will not and neither will a stove, a macbook or a fancy smart home system. They are part of our live, loose value and we accept that.
But solar or batteries (granted, mostly with home-solutions)? Better make money, otherwise why even bother.
- Fridge: has ROI vs. going to the store more often or getting food poisoning.
- Washing machine: Has ROI measured in the value of your time spent not slapping clothes against a board to make them clean.
- Stove: ROI vs. using and maintaining a fire pit, with the risk of burning your house down factored in.
- MacBook: ROI is how much work you can get done vs. a Windows machine, or not having a laptop and doing math really fast by hand on paper.
Etc. It is suspicious that there isn’t a “this will pay for itself in N years vs. not having it” statement somewhere.
And of course it isn't a risk-free return.
Consider what happened to investors in Germany, Hungary, or Romania in the 01930s, or South Vietnam in the 01960s, or Afghanistan in the 01970s, or Iraq in the 01990s.
You might think this is irrelevant because you don't live in 01930s Germany or 01970s Afghanistan or 01990s Iraq; you live in the USA.
But, if you live in the USA, you don't live in the USA of the 01970s or the 01930s. You live in the USA of 02025. In 02025, the country most like 01930s USA or 01970s USA is China, which is obvious if you read books from the USA from those periods. The USA in 02025 is the country that's been trying and failing to build high-speed rail for 60 years, since Japan got it working, and just elected a xenophobic demagogue who praises dictatorship; it's much more like 01980s Russia or 01930s Italy.
Warren Buffett said that, in the long run, you can't expect the stock market to return more than the long-run economic growth rate, which you can't expect to consistently be more than 3%. I don't understand the logic behind either of these propositions, but I suspect Buffett knows more about market returns than I do.
— ⁂ —
By contrast, if you can get an 0.8% discount on the potatoes your family eats by bulk-buying enough potatoes for the next three months, that's about a 10% annual return on investment, and the risk is pretty low—and almost entirely under your control. And, in practice, you can often get a much bigger discount than that, especially if you assign some cost to the errand of going potato shopping. You just have to make sure you have proper potato storage and that you don't have a sudden dropoff in family potato consumption.
How do I figure that ROI? Well, the amount of extra money you have tied up in potatoes oscillates between two months' worth and zero, with an average of one month of potatoes. But your expenditures on potatoes are 0.8% less each month, which is your earnings from that investment. Every year, you save 10% of a month of potatoes: 10% of your investment. Tax-free.
If you learn to calculate ROIs and reorganize your household expenses on the basis of ROIs, whatever income you have will go dramatically further than it would for someone who hasn't done that.
The thing is, I'm unsure whether this holds true. Could you actually replace pipes inside a huge sand battery without bringing the entire thing offline? And at some point are you basically rebuilding it?
Internet akchually: a small amount of the heat will be dropped in the wiring that forms the short circuit rather than in the internal resistance. So the panel will be slightly cooler than you'd expect for an object of that colour even in short circuit. They're the same temperature in open circuit, though. When operating normally, they can be quite a lot cooler and in fact you can detect non-functional panels by looking for hot ones with thermal cameras.
I did know that normally-operating panels were significantly cooler (23% efficiency means 23% less heat than a regular black body) but I had no idea that people used this feature to detect broken panels with thermal cameras. I'd only seen people forward-biasing the panels from an external source to stimulate NIR light emission and using NIR cameras.
I guess oil is too valuable to just burn.
So, at equal cost, the alternative to a megawatt of windmills may not be a megawatt of solar panels, but 10 megawatts of solar panels. And that can compensate for their lower capacity factor.
I don't think people are building gas-powered data centers in the US. There's a data center crunch in the US because people aren't building them because they can't get the power because of the US's anti-renewable-energy policies.
And I don't think it's accurate to say, "this is a first-time installation of a new technology that hasn’t scaled". People have been using thermal energy storage for household heating for literally millions of years. https://en.wikipedia.org/wiki/Thermal_mass https://en.wikipedia.org/wiki/Thermal_energy_storage https://en.wikipedia.org/wiki/Storage_heater https://en.wikipedia.org/wiki/Ondol#Advantages_and_disadvant... https://en.wikipedia.org/wiki/Seasonal_thermal_energy_storag... https://en.wikipedia.org/wiki/Masonry_heater https://en.wikipedia.org/wiki/Ground_source_heat_pump https://en.wikipedia.org/wiki/Trombe_wall https://en.wikipedia.org/wiki/Feolite https://en.wikipedia.org/wiki/Drake_Landing_Solar_Community https://en.wikipedia.org/wiki/Kang_bed-stove https://en.wikipedia.org/wiki/Earthship#Thermal_performance https://en.wikipedia.org/wiki/Rocket_mass_heater https://www.helen.fi/en/news/2018/Gigantic-cavern-heat-stora... https://en.wikipedia.org/wiki/Barra_system https://en.wikipedia.org/wiki/Storage_heater https://en.wikipedia.org/wiki/Earth_shelter#Active_and_passi... https://en.wikipedia.org/wiki/Bokpoort_CSP#Energy_storage https://en.wikipedia.org/wiki/Russian_stove#Design https://en.wikipedia.org/wiki/Passive_solar_building_design#... https://en.wikipedia.org/wiki/Aquifer_thermal_energy_storage https://en.wikipedia.org/wiki/Home_energy_storage#Thermal_en... https://en.wikipedia.org/wiki/Qanat#Cooling https://en.wikipedia.org/wiki/Regenerative_heat_exchanger https://en.wikipedia.org/wiki/Rammed_earth#History https://www.mha-net.org/ https://en.wikipedia.org/wiki/Solana_Generating_Station#Ener... https://en.wikipedia.org/wiki/Hot_water_storage_tank
The people who would mostly benefit from reduction in emissions - especially in the short term - are those in other countries. It's not going to be Finland suffering the most from doubling of the cost of food from failed harvests, it's going to be massive failures in rice harvests in south east asia. Finns will always be able to outcompete the average Cambodian when buying food.
One of the costs of emissions to western countries - say Spain - is increased bad weather - more frequent storms, fires etc. All fairly small stuff compared with mass starvation or water shortages though. That starvation leads to another problem -- increased migration pressure.
But those costs are going to be borne anyway. Even if Spain stopped emitting CO2, it wouldn't make an ounce of difference. International agreements have failed time after time to curb emissions.
The main benefit of renewable energy for a given country isn't the reduction in emissions, it's the increase in energy independence - no need to import gas or oil from unstable countries.