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250MWh 'Sand Battery' to start construction in Finland
- penissucker4167 11mo ago[dead]
- nightshift1 11mo agoInteresting. Does anyone know what source of electricity is going to be used for this ? Probably solar but it might be also useful with coal plants or wind farms that produce even when there is not enough demand. How are they moving the heat ?
- whizzter 11mo agoSee my other comment about Nordic power balancing.
- crishoj 11mo agoIt's a heat battery for district heating. Could be other sources than electricity, e.g. municipal garbage incineration plant.
- Maxion 11mo agoNo, these generally use excess power during the night and windy days to store heat. There's not that much CHP production that there'd be excess, plus they can adjust those plants well enough that there's no unnecessary burning going on.
- fulafel 11mo agoThere's water based heat batteries (aka thermal storage caverns) that are supplied with district heat in use in other places, but this is not one of them. The article says "Polar Night Energy’s technology works by heating a sand or a similar solid material using electricity"
- perihelions 11mo agoNatural gas and wood chips, > "The installation will supply heat to the Vääksy district heating network and is expected to lower fossil-based emissions by approximately 60% annually, primarily through an estimated 80% reduction in natural gas consumption and reduced reliance on wood chips." https://www.pv-magazine.com/2025/11/25/finlands-polar-night-to-build-250-mwh-sand-battery-for-district-heating-provider/ https://www.pv-magazine.com/2025/11/25/finlands-polar-night-...
- jonners00 11mo agoThose are the energy sources they're replacing with this tech - according to <https://reneweconomy.com.au/new-worlds-largest-sand-battery-to-double-the-size-of-current-record-holder/ https://reneweconomy.com.au/new-worlds-largest-sand-battery-...> it's surplus energy from renewables that will 'charge' the battery (so likely wind, hydro and solar that is produced but surplus to the grid's requirements)
- Hamuko 11mo agoMost likely not solar since there’s almost no solar during the winter months. Sun comes up at 0900 and goes down at 1500 in the south. In the north it’s worse. It's currently noon in Finland and solar accounts for 6 MW in the grid. That's about 0.05% of the total production. Nuclear is 3863 MW (~31%) and wind is 6281 MW (~50%). What might be plentiful is wind, especially during the nights.
- anttisalmela 11mo agoWind in practice. There's only few hours of sunlight in the winter during the day. There has been a surge of electric boiler buildup by district heating companies in the last few years to exploit the periods of high wind and resulting very low electricity prices. Heat is transferred using disctrict heating networks where 65-120 C water is circulated.
- retrac 11mo agoThere's an interesting property to thermal storage, as a consequence of simple geometry. Consider a cube. volume = n³ and surface area = 6*n². Surface area increases more slowly than volume. The ratio of surface to volume decreases with more size. Thus: a sufficiently large thermal reservoir becomes self-insulating with its own mass.
- amelius 11mo agoYeah but if you transfer the energy as heat then you will end up with elongated structures (pipes).
- jfengel 11mo agoIs that a problem? Pipes are not technically complicated. Is there something else I'm missing?
- kees99 11mo agoLarger storage structures are easier to (thermally) insulate. Because geometry. But going with larger structures probably means aggregation (fewer of them are built, and further apart). Assuming homes to be heated are staying where they are, that requires longer pipes. Which are harder to insulate. Because geometry.
- crazygringo 11mo agoI can't help but wonder how the efficiency compares to generating electricity, running that over wires, and having that run heat pumps. The conversion to electricity loses energy, but I assume the loss is negligible in transmission, and then modern heat pumps themselves are much more efficient. And the average high and low in February in 26°F and 14°F according to Google, while modern heat pumps are more energy-efficient than resistive heating above around 0°F. So even around 14–26°F, the coefficient of performance should still be 2–3.
- 11mo ago
- whizzter 11mo agoFor reference, this city is about as north as Anchorage Alaska and today they got less than 7 hours of sunlight and it'll continue to decrease for the next 3 weeks. The Nordic countries generally still wants to increase their wind and solar power, but the big issue during winters is when there's cold air high pressure systems we get neither sun nor wind, having an energy storage that can hold up to 5 days worth of energy should help us nudge past them. Hydro-energy exist (mainly Sweden and Norway, but I think some in Finland as well), but it's fairly built out so stable non-fossil power needs to be nuclear, or wind/sun + storage (that hasn't been good enough so far).
- dofdial 11mo agoinvest in saving/harvesting energy. Better than producing when solar is cheap as hell and you get no-solar-harvesting because of your location
- bryanlarsen 11mo agoHydro energy generation is fairly built out, but the Nordics have lots of places suitable to build out hydro energy storage. Hydro generation requires a flow to dam, but storage doesn't.
- magicalhippo 11mo agoTrue, but that disrupts ecosystems. Or so the argument against go building storage dams go. That said, there's been a fair bit of talk here in Norway recently about tax incentives blocking hydro owners from upgrading old generators, improving efficency. Apparently a lot of currently unused power available if they "just" did that.
- tempestn 11mo agoI wonder if it's possible to also increase the amount of generation on existing dams? I could imagine there being situations where there's excess peak flow capacity but it isn't utilized because the flow rate would be unsustainable. But if we're looking for storage it could make sense.
- apatheticonion 11mo agoI was interested in trying to make a DIY thermal battery as a hobby experiment. Other than using thermal energy directly, I couldn't find a way to effectively convert the heat energy to electrical energy. Peltier modules can be used to generate electricity, but they are crazy inefficient. An efficient steam turbine is largely inaccessible to hobbiests and I am scared of steam/pressure. Though I did look at repurposing a car turbo for this purpose. There were additional issues with regulating the amount of heat you wanted to extract (load matching) and recycling waste heat. I wondered if it was possible to use a Sterling engine, but you can't buy anything other than very small toys online and I don't have the facilities to machine my own. Haha, would love to get something working, but I suppose I'm not smart enough to figure out an effective way to get that heat back out as usable/controlled electricity.
- PaulKeeble 11mo agoThe answer in almost all electrical production boils down to spinning a turbine with steam (or wind). Nuclear does it, all the fossil fuels do it and ultimately heat batteries do it too. The alternative is photovoltaic or directly nuclear to electron production and then storage with chemical batteries or massive capacitors. Most of our electrical production is based on a solution found several hundred years ago, we just made it really big and worked out how to control the heating and pressure of the steam well.
- chii 11mo agoYou missed thermoelectric generators that uses the Seebeck effect to generate a current between two temperature differentials. It's terribly inefficient, unfortunately.
- baq 11mo agoNon-steam turbines have been operated (e.g. https://en.wikipedia.org/wiki/Mercury_vapour_turbine https://en.wikipedia.org/wiki/Mercury_vapour_turbine), but… steam is just so much easier to work with.
- 11mo ago
- octaane 11mo agoIt's probably my ignorance about this sector, but I do find it impressive that they are getting that much storage capacity in a small area: > "This latest project will use locally available natural sand, held in a container 14m high and 15m wide."
- killingtime74 11mo agoAI says this volume will hold about 4000 tonnes of sand. Hence the high capacity.
- pythonguython 11mo agoA website called energy-storage dot news should not be mixing up energy and power
- supernova87a 11mo agoI was surprised too at the 2nd sentence: "The project will have a heating power of 2MW and a thermal energy storage (TES) capacity of 250MW..." and how a news outlet about energy could get such a fundamental unit wrong. But given that later in the article it does revert to correct units (and the numbers are plausibly proportional), I assume it's just a typo. Strange that it hasn't been corrected even now. "...It follows Polar Night Energy completing and putting a 1MW/100MWh Sand Battery TES project into commercial operations this summer..."
- pfdietz 11mo agoThese are interesting, but the cost per kWh of storage capacity is still probably too high for true seasonal storage. Short term storage runs into competition with batteries. I point again to Standard Thermal for an idea tailored to true seasonal storage. I wait for more news from them, particularly on their very low cost resistive heater technology. https://www.orcasciences.com/articles/standard-thermal https://www.orcasciences.com/articles/standard-thermal
- MBCook 11mo agoBut thermal storage doesn’t wear out, unlike batteries, right? So less future maintenance. Plus there is no danger of battery puncture. More directly this is a very cold area. Enough it might effect battery storage enough to be a real problem.
- pfdietz 11mo agoI'm not sure why you think not wearing out would necessarily make up for the capex being too high. Interest rates aren't zero.
- degamad 11mo agoNot wearing out increases the time frame across which you can amortise the costs. If option A costs $100,000/unit and needs to be replaced every 10 years, while option B costs $300,000/unit but lasts 50 years before replacement, option B is still cheaper in the long run, even factoring in interest rates. (You can substitute "time until replacement" in the above with "time until maintenance costs exceed the original capex", and the logic remains the same.)
- happosai 11mo agoDoesn't need to be seasonal, we have enough energy in general to go through winter. This is to help through week long cold snaps, when Finland is short on energy. Week-long storage is still eyewateringly expensive with chemical batteries. Also the capex from sand battery goes to (mostly) local construction, while when buying chemical batteries all the money goes to china.
- Ericson2314 11mo agoEU is going to have to either - embrace nuclear - embrace North Africa, admitting them as member states, and doing massive solar there, and doing massive grid expansion to carry it north. And then in top of that, will their way to sufficient storage like the rest of us. We'll see what they choose :D
- energy123 11mo agoEU does have trouble with solar seasonality, but wind is seasonally anti-correlated with solar, and the geospatial correlation between different wind turbines drops off more than linearly with distance, and the EU covers a very large land mass as-is. You can also over-build solar inside Europe to have reasonable collection during winter. I also see no reason to admit North African states into the EU before an agreement can be reached about transporting solar. The geopolitical risks have always been about other states severing the link during a conflict with you, and less about the parties to the deal reneging. So whether Morocco or Algeria is part of the EU is quite immaterial to the risk profile. This kind of thing really does need simulation modelling to be reasoned about properly. The one thing I am confident in saying is that these single sentence just-so stories about what is and isn't a good idea are going to be wrong, because the fundamental principle is statistical diversification, which needs to be approached through simulation rather than through words.
- pfdietz 11mo agoHere's your modeling site: https://model.energy/ https://model.energy/ It's helpful to have two flavors of storage; one short term and efficient (batteries), one long term with low capex (hydrogen, thermal). The last is the most undeveloped but there are promising ideas.
- myrmidon 11mo agoThis is really interesting. I put some numbers into this, and the required power for long term storage is significantly lower than I'd have expected. This was giving me for Germany (assuming 80GW of constant demand) under 50GW of required hydrogen turbine power (35GW of gas turbines are already installed, but only a fraction H2 ready). Overprovisioning (wind/solar) is suprisingly high, with 180GW of wind and 440GW of solar. Currently installed capacity for those is about 30% of that. Short-term storage capacity is a really big gap though (the model suggests 750GWh, and currently there's <30GWh installed). In conclusion: Under pessimistic simplifications, Germany is at about 30% progress toward fully renewable electricity (but battery capacity is lagging behind). Assuming wind/solar buildout continues at rates comparable to the last decade, this would mean zero-emission electricity in ~35 years. Could be worse. But I'm personally bracing for 2-4°C of warming, and don't think european glaciers will survive the next century...
- deleted 11mo ago[deleted]
- ionwake 11mo agoI like how sand batteries are the equivalent of sleeping on the ashes of your fire
- pcdoodle 11mo ago[dead]
- deleted 11mo ago[deleted]
- tonyhart7 11mo agoI never see sand battery before between this and salt battery which one is the future???
- Mashimo 11mo agoAFAIK sandbattery is simpler (for district heating) and thus cheaper.
- bochoh 11mo agoIn a cold climate, I would expect burying it to use the ground as a natural insulator. Why was an above ground design chosen? Specifically, does the need for heavy insulation and the active heating of the sand make the ground a less effective or even problematic insulator? Could excavating and building a below-ground foundation for a high-temperature device like this be more complex and expensive than an above-ground silo? How would permafrost conditions affect this design?
- Maxion 11mo ago> Why was an above ground design chosen? Because digging is expensive and there's plenty of land. More efficient to use the budget to build a bigger structure than to build a smaller one and dig down. Bigger structure also gives you better insulation (surface area compared to volume decreases non-linearly with increased volume).
- jillesvangurp 11mo agoAlso, digging in sand is easy. But blowing up granite isn't. The Ice age stripped a way a lot of soil in Finland.
- Hamuko 11mo agoWe’re pretty accustomed to building underground in Finland. You can find all sorts of English-language articles about it. https://abcnews.go.com/International/helsinkis-underground-city-reflects-tense-position-russias-neighbor/story?id=84668764 https://abcnews.go.com/International/helsinkis-underground-c...
- xarope 11mo agowould someone give an ELI5 on how a sand battery works? Is it just purely thermal mass, just with tons of sand?
- andsoitis 11mo agoYou use electricity (ideally cheap solar/wind) to heat air. That hot air circulates through a silo full of sand. The sand holds the heat for months. Later the heat is drawn out and used for buildings or industrial processes.
- deleted 11mo ago[deleted]
- jabl 11mo agoThere's pipework for circulating air inside it when they want to charge/discharge it, but yes, essentially it's mostly tons of sand. They have resistors for charging it with electricity (resistors heat the air, air is circulated in the pipes which heats the sand) when the electricity price is cheap, and then for discharging they have a air-water heat exchanger so they can pump the heat energy into the district heating network.
- OvervCW 11mo agoWhy do they use air for this instead of water?
- deviation 11mo agoLikely a combination of practicality, and the importance of airflow throughout the sand in order to heat it and pull from it effectively. Also, water's specific heat capacity is 4.186 J/g°C, while air's is approximately 1.005 J/g°C. It would take much more energy to heat up water than it would to heat up air. Also, water boils at 100 degrees, and they store it in the sand at 600 degrees.
- ggm 11mo agoWhy do so many people do "why didn't you..." As if the engineers who designed this didn't have 1002 alternatives and went with this one for reasons of budget, politics, prior knowledge, IPR costs, skills, religious beliefs, or a million other reasons. Why did we go to the moon when we have perfectly good vacuum chambers here at home. The implied "my way is better" in these responses is usually the bad take on "what made this better than my way" as a question which nobody really can answer unless the OP is the engineer. "Why does Finland not deploy ubiquitous small nuclear reactors every 25 meters and make a heated road to the north you can drive over as well as get power from if you have a power adapter for finnish plugs"
- chickenbig 11mo agoThe big question is how much it will cost. For comparison I believe there is a heat battery in Germany using (atmospheric pressure) liquid water (98 C), 50M EUR for perhaps 20x the thermal storage capacity (versus 20 C water). The use of sand, presumably heated to a much higher temperature than the boiling point of water, seems overkill for district heating (unless peak heat demand requires flow temperatures above 100 C). But it does reduce the volume of sand required, so the size of the storage system.
- jillesvangurp 11mo agoThe cost is a function of the size and mass. So, more heat capacity and less mass means lower cost per mwh. These things are extremely simple and fairly efficient. It's resistive heating (wires and spools) of a thermal mass (sand/stone) in some kind of container (a simple silo) with a lot of insulation and some pipes to heat up water. Higher temperatures mean getting the heat out is easier and that the battery will work for longer. Basically until the temperature drops below the required temperature.
- Ekaros 11mo agoRequired temperature is 65 to 115... If you are already above those you only need simpler and cheaper heat exchanger instead of more complex heatpump.
- chickenbig 11mo ago> So, more heat capacity and less mass means lower cost per mwh. Can you compare different technologies with these scaling laws? Also what are the limits of these approximations (e.g. taking temperatures to extremes tends to run into maintenance problems). In this case the sand battery delivers 400 C steam from 600 C sand [0], via some heat exchange fluid (solar salt?) that flows next to the sand. Going through heating/cooling cycles can cause material issues, especially for larger temperature differences. [0] https://polarnightenergy.com/sand-battery/ https://polarnightenergy.com/sand-battery/
- Hamuko 11mo ago>The use of sand, presumably heated to a much higher temperature than the boiling point of water 600°C according to their website.
- timonoko 11mo ago[flagged]
- kalaksi 11mo agoThere wasn't much about the energy equation there. And since it's just conversation with Gemini just pasted here, I'm not sure how much to trust it and it just feels lazy and disjointed.
- deleted 11mo ago[deleted]
- timonoko 11mo agoFinland's current energy equation according to Google Gemini: Is Finland importing household garbage from Italy and why? Gemini: ... In summary, Finland imports waste (mainly as pre-processed fuel) to feed its modern waste-to-energy plants, which are a key part of its heating and energy strategy, especially as domestic residual waste volumes decrease due to better recycling and as a replacement for former Russian renewable fuel imports. Why you call it "processed"? It is raw garbage in huge mounds smelling bad and harboring flies and rats? Gemini: ... This processing turns smelly, inconsistent "garbage" into a stable, high-quality, non-hazardous secondary fuel that is compliant with strict EU waste shipment and energy production regulations. The whole point of the import is to fuel power plants efficiently, which requires this specific, processed product. Lets try again. Why the "processed" mound of garbage from Italy smells bad and houses flies and rats? Gemini: ... Sometimes .... This is not "sometimes", it makes living near Loviisa harbour impossible. Gemini: ... It is clear that the environmental integrity and quality of life for residents of Loviisa have been compromised by the need to fuel Finland's waste-to-energy capacity with large, sometimes substandard, imports. etc etc. === Short summary: The Pro-Russian Green "Pedophile"-Party destroyed the existing energy infrastructure which ran on coal from Poland etc. A new system was built to use "renewable" Russian gas and Russian wood industry leftovers. The situation is desperate; any shit from anywhere at any cost is better than using local renewable biomass, such as peat. Finland has enormous amounts of peat, which is worth more than Norway's oil reserves.
- timonoko 11mo agoPedophiles were insulted, I am sorry. Correct English expression is maybe "Baby Lovers"? I dont know.
- fsloth 11mo agoThe comment is slightly incoherent in it's argumentation, but factually correct. I think the point is the energy policies in some of the nordics are as arbitrary and politics driven as anywhere. How this is directly related to the sand battery is not clear to me, but it does paint an accurate if partial picture of the milieu.
- cess11 11mo ago
- nickdothutton 11mo agoThose of us in the UK will recognise this as a giant "Economy 7 Night storage heater".
- rsynnott 11mo agoI do kind of wonder will those come back, with a slightly smarter heuristic for turning on than "it is night". They're inefficient next to a heat pump, but vastly cheaper to make and install, so with a smarter grid, they may be an appropriate sink for excess solar/wind in times of overproduction.
- tempodox 11mo agoThis is great news! Congrats for this fantastic progress.
- kineticdaffodil 11mo ago[dead]