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Finnish City Inaugurates 1 MW/100 MWh Sand Battery
- slumpvaldperson 1y agoVery interesting. Did anyone find a ROI calculation?
- theshrike79 1y agoIt's a prototype, so not really relevant.
- flanked-evergl 1y agoIf 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.
- jonespen 1y agoSo, a gigantic sauna heater? Very on brand Tommi and Markku!
- fulafel 1y agoIt doesn't list the advantages over water, which seems the most common in https://en.wikipedia.org/wiki/Thermal_energy_storage https://en.wikipedia.org/wiki/Thermal_energy_storage systems. 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.
- isoprophlex 1y agoFor 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 1y agoI wonder if there are any chemical effects from heating the sand to 500 degrees Celsius. Finely roasted sand.
- isoprophlex 1y agoNone, 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.
- LtdJorge 1y agoIt's as inert as it gets
- grues-dinner 1y agoThis is crushed soapstone, so it's mostly talc. Talc is apparently more or less stable up to about 800C, where it starts to break down into enstatite and silica: https://nvlpubs.nist.gov/nistpubs/jres/15/jresv15n5p551_A1b.pdf https://nvlpubs.nist.gov/nistpubs/jres/15/jresv15n5p551_A1b.... 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 1y agoInteresting, thanks for pointing that out, I didnt catch that they're not using actual sand.
- Puts 1y agoHelsinki did the same thing but storing the energy in water instead of sand: https://helsinkismart.fi/worlds-largest-cavern-thermal-energy-storage-built-in-vantaa/ https://helsinkismart.fi/worlds-largest-cavern-thermal-energ...
- anttisalmela 1y agoSeveral 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.
- nabla9 1y agoHelsinki 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.
- napoleoncomplex 1y agoFor anyone interested in a breakdown of the basic logic, this recent blogpost that trended on HN is probably the best: https://austinvernon.site/blog/standardthermal.html https://austinvernon.site/blog/standardthermal.html Really interested in seeing how it fares in reality, almost sounds too good to be true.
- jnsaff2 1y agoWhy 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.
- HPsquared 1y agoYeah the efficiency is much less than 40% if you compare to heat pumps. It'll be something like 15% compared to those.
- Sharlin 1y agoThe 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.
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- kitd 1y agoI 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 1y 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 1y agoI 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 1y agoAre 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.
- lupusreal 1y agoAs 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 1y agoTo 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.
- petesergeant 1y agoI 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.
- Cthulhu_ 1y agoIn 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.
- phh 1y agoWell 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.
- dzhiurgis 1y ago> you can't really do -600C sand (or anything) You can if you stagger AC/HP or even peltier elements.
- Gravityloss 1y agoYou 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.
- Havoc 1y agoInteresting capacity vs discharge ratio. Way slower than battery but presumably sand scales well
- Fwirt 1y agoInterestingly 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_ 1y agoSo why a surface sand silo instead of going down and using the soil/clay/bedrock/whatever is there? Ease of installation and maintenance?
- whimsicalism 1y agopresumably you need the insulation from the air, otherwise it would just sort of dissipate through the ground
- Findecanor 1y agoI'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.
- IshKebab 1y agoOpen 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.
- whimsicalism 1y agoi 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
- IshKebab 1y agoI said open air.
- whimsicalism 1y ago
- Cthulhu_ 1y agoRelated: in Sweden they filled a cave (an old mine?) with water and are using that as heat storage: https://www.youtube.com/watch?v=VSdKL0Nnk-k https://www.youtube.com/watch?v=VSdKL0Nnk-k
- pintxo 1y agoReally 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 1y agoSweden seems to have some of the highest "Electricity consumption per dwelling" (https://www.odyssee-mure.eu/publications/efficiency-by-sector/households/electricity-consumption-dwelling.html 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?
- lysace 1y ago16 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.
- pintxo 1y agoGermany, 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.
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- dzhiurgis 1y agoWonder 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 1y agoStaggering 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.
- bjoli 1y ago90% roundtrip efficiency is pretty darn cool. I am not an engineer, but is it the high temperature difference that makes that possible?
- smokel 1y agoThat's only in heat transfer, that does not include generating electricity from it.
- IshKebab 1y agoI 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.
- arowthway 1y agoThis is super cool but the ending is bizarre. > 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.
- ta1243 1y agoPeople 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
- testdelacc1 1y agoI 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.
- Avamander 1y 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.
- dguest 1y agoFinland 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. [1]: https://ourworldindata.org/grapher/energy-consumption-by-source-and-country?country=~FIN https://ourworldindata.org/grapher/energy-consumption-by-sou...
- Hikikomori 1y agoMost 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).
- myrmidon 1y 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. 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".
- dguest 1y agoI think the primary energy does include electric generation, but you're right, I posted the wrong chart. The correct one is here: https://ourworldindata.org/grapher/electricity-prod-source-stacked?stackMode=relative&country=~FIN 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.
- phtrivier 1y agoIt 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 ?
- lupusreal 1y agoThey already have district heating.
- jpalomaki 1y agoOver half of Finland’s population lives in buildings connected to district heating.
- Ekaros 1y agoFinland 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.
- davedx 1y agoGood 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?
- grues-dinner 1y agoFinland 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)
- flowerthoughts 1y agoW 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 1y agoI dunno, 1kWh seems quite natural as a unit of building-scale energy usage when you know a kettle or space heater is about 3kW. We think about energy usage much more in terms of kW and hours than in watts and seconds. And even in small devices like an LED bulb, 5W is more obviously 0.005kW than, say, 2 hours is 7200 seconds. 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.
- anovikov 1y agoProblem 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...
- shellfishgene 1y agoIn the end it may still make financial sense, the price for electricity often goes down to near zero or even below.
- haspok 1y agoThis is not a battery, this is thermal storage. No electricity is stored or generated. (Unlike liquid-metal batteries, for example, which are actual battery storage.)
- deleted 1y ago[deleted]
- alkonaut 1y agoNo one is claiming it is storing electricity. I think people who use imperial (BTU) units for heat but SI units for electric power some times get confused by what power really is and what a battery is. 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.
- credit_guy 1y agoIt's not clear to me why you would hold 100 hours of energy, assuming you discharge at maximum power. If you want to store energy from summer to winter, then 4 days of energy is nothing. Even if your average discharge is only 30% of the maximum power, you still get only 2 weeks of energy. And if the use case is day to night, then 8 hours of storage is enough. Maybe the idea is that the houses in Finland are so well insulated that you need heating only in cases of extreme cold, and only during the night, 100 hours will do the job?
- etrautmann 1y ago4 days is often cited as a useful target for buffering power to backstop intermittent generation from renewable sources. You're never going to store a full winter's worth of power, and might want to be able to ride out a few days of weather.
- rajnathani 1y agoPrevious discussion (104 points | 27 comments) from 79 days ago before the inauguration: https://news.ycombinator.com/item?id=44295132 https://news.ycombinator.com/item?id=44295132