For 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.<p>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.<p>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).
One of the interesting things about hydro is that it's usually constructed to satisfy baseload power. In reality, shifting that over to a peaking plant requires relatively modest changes to system, a small fraction of the cost of an entirely new dam. You don't actually need the "Pumped" part of pumped hydro, you can just throttle normal hydro on and off if you have enough turbines (though for ecological & geomorphological reasons some minor downstream damming also helps). There wasn't any reason to install the extra turbines in the age of fossil fuels. They only take ~30 seconds to spin up, versus days or weeks for thermal plants.
> <i>“Hydro-energy exist, but it's fairly built out so stable non-fossil power needs to be nuclear, or wind/sun + storage”</i><p>Interconnectors also exist (and more are planned), which means, for example, that Norway can buy wind energy from the UK when it’s cheap and abundant, in preference to using stored energy from their hydro lakes.<p>That way they effectively get more out of existing hydro lakes, which in Norway is already a very significant storage capacity.
Theres not going to be built any more interconnectors from Norway anytime soon.<p>Electricity became a lot more expensive in Norway after building several interconnectors to UK and mainland Europe. Importing high prices from the failed energy politics of UK and Germany which both have among the most expensive electricity in the world.<p>This has been a huge debate, and the general concensus seems to be that joining ACER and building inrerconnectors to mainland Europe was a big mistake.
Does that mean Norway is making a huge amount of money exporting electricity over those interconnections?
That seems counterintuitive to me.<p>Electricity prices don't go up because you have access to expensive power, it goes up because you don't have enough cheap power so you have to buy the expensive power.<p>It seems like Norway just wouldn't have power if they weren't connected to other sources, not that they'd have more cheap power.
Electricity prices go up when you have access to customers who are willing to pay more. If grid connections to other regions are limited, people in regions with a lot of cheap generation (such as Norway) pay low prices. But if you add grid connections without increasing generation capacity, prices start equalizing between regions, as every power company tries to sell to the highest bidder.<p>Norway could power itself fully with domestic hydro. But it chose not to, as the power companies make more money by importing foreign power when it's cheap and exporting hydro when it's not.
Washington state has the same problem to a lesser degree. California pays more for cheap Washington hydro, which causes the costs to go up for us, although I guess not as drastic as Norway since our electricity is still considered cheap.
> "Norway could power itself fully with domestic hydro."
We have events where the we cannot get enough load from domestic production. Typically in winter when water freezes.
> It seems like Norway just wouldn't have power if they weren't connected to other sources, not that they'd have more cheap power.<p>This is not the case as Norway and neighbouring Sweden have plentiful hydro. It's especially valuable as it can be regulated to complement wind/solar fluctuations, essentially replacing storage.
Obviously the presumably large amount of money spent to interconnect could have been spent adding local production and storage. It would be a waste of money if there was a reasonable path to local energy independence that was neglected.
A significant proportion of Norway's domestic energy production is hydro, which comes with it's own "built in" storage up to the capacity of the dams, so Norway already has a very significant storage capacity.<p>Estimates suggests a storage capacity of 87TWh of storage in hydro reservoirs, compared to production capacity in recent years between 146 and 157 TWh, and a theoretical production capacity of ~309TWh (I don't know the basis for that - I'd imagine peak production at all the plants, but I doubt that could ever happen in reality, so the 146-157TWh based on real production are better...)<p>Compare that to Norwegian electricity consumption of 124 TWh in 2020.<p>Of course, since so much of Norways total electricity production is hydro, large storage is <i>necessary</i>, as the hydro supply is highly seasonal, based on e.g. things like the amount of melting snow in the mountains in spring.
It’s basic supply and demand. And by linking to other grids, you increase demand since there’s now more customers for your supply. What they have (comparatively) less is supply since the supply in those markets is shite in comparison to what Sweden and Norway have for their local demand.
> Norway can buy wind energy from the UK<p>Even Southern England cannot get enough wind energy from Scotland to fully utilise wind farms because transmission capacity is insufficient. I would imagine a transmission line to Norway will be even more expensive than to England.
Solving the Scotland/England interconnect under-capacity is well underway <a href="https://en.wikipedia.org/wiki/List_of_high-voltage_transmission_links_in_the_United_Kingdom" rel="nofollow">https://en.wikipedia.org/wiki/List_of_high-voltage_transmiss...</a>
But they are building such a link, because it'll make/save more money than it costs.<p>Imagine how many doom and gloom headlines we'd have avoided if these two massive construction projects could have been sync'd up perfectly or if we had a national press that could do anything other than try to scare people with big numbers.
The interconnects already exists.
> the big issue during winters is when there's cold air high pressure systems we get neither sun nor wind<p>Wind does better in the winter.<p>See eg here for Canada monthly stats: <a href="https://www150.statcan.gc.ca/t1/tbl1/en/tv.action?pid=2510001501&pickMembers%5B0%5D=1.1&pickMembers%5B1%5D=2.1&cubeTimeFrame.startMonth=07&cubeTimeFrame.startYear=2024&cubeTimeFrame.endMonth=05&cubeTimeFrame.endYear=2025&referencePeriods=20240701%2C20250501" rel="nofollow">https://www150.statcan.gc.ca/t1/tbl1/en/tv.action?pid=251000...</a><p>Also, wind does better at night than day, which may be related or not.
I think the point is that winter can create periods where there is neither adequate wind or adequate sun. Having strong wind production at some times will only be good if there's a way to store the excess. That's exactly what this project does and I believe that was GPs point.
And in Finland: 60% of Finnish wind energy 'collected' in the winter months (Oct-Mar)<p><a href="https://suomenuusiutuvat.fi/en/wind-power/wind-power-in-cold-temperatures/" rel="nofollow">https://suomenuusiutuvat.fi/en/wind-power/wind-power-in-cold...</a>
> there's cold air high pressure systems we get neither sun nor wind<p>AKA <a href="https://en.wikipedia.org/wiki/Dunkelflaute" rel="nofollow">https://en.wikipedia.org/wiki/Dunkelflaute</a>
Hydro 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.
We don't really. Hydro storage requires reservoirs where you can freely adjust the water level. Most of our lakes have shorelines that have been built out, and the property owners get really angry if you suggest frequently adjusting the water level significantly.<p>The largest planned hydro storage projects are using decommissioned mines, and those are going to run out quickly.
You could just build a back-channel for the existing hydro-dams? Those reservoirs are only full for a short period and that is when you dont need pump energy.
But where? In Finland, at least, the land is relatively flat when compared with Norway and Sweden, and with a large rural population there aren't really any good locations.<p>In my local area, we had major flooding this spring because the hydro plant operators were sleeping on the job (or whatever they did instead of regulating water levels). And that was a simple 2m increase in water levels.<p>NO/SE have some more geographically suitable locations, but last time I checked, flooding them was considered too environmentally destructive too the local environment.
Yeah, you're right regarding the environmental concerns.<p>Most of Norway's hydro dams were built a long time ago when there was little focus on the environmental effects.<p>The last major plant went live in 1993. Most of the focus now is on far smaller schemes, that doesn't really add up to a lot compared to Norway's established generating capacity (which outstrip the total electricity use anyway), but which also meet far less opposition.<p>Part of the reason for that was growing local opposition to larger plants, and sometimes national opposition, culminating with the Alta controversy[1] in the late 70's that were some of the largest civil protests in Norway since the end of WW2. The protests eventually failed, but it had a lasting effect on Norwegian politics.<p>[1] <a href="https://en.wikipedia.org/wiki/Alta_controversy" rel="nofollow">https://en.wikipedia.org/wiki/Alta_controversy</a>
If you pump the water back into the existing reserviors you will have less flooding?<p>I suggested a pump-water extension to existing hydro power reservoirs.<p>Like your EV recharges when you release the pedal.<p>Right shouldn't talk about EVs with a Finn, that analogy will not fly. Ok, like if you plan carefully where you throw up your koskenkorva you can re-use it.
The reservoirs in Finland aren't quite at the scale your Explorer Vodka-fuelled Swedish mind believe them to be. Most are small generators hooked up to the local rivers, and are required to prioritize keeping the water from flooding residential areas.<p>There's a reason we're looking at using old mines for pumped hydro rather than trying to pump water upriver during a spring flood because other power sources have surplus generation.
You could use the ocean for the bottom level and an artificial reservoir for the top level. You're not going to noticeably affect ocean levels.<p>Or just use a large lake. You're not going to noticeably affect the water levels of a large lake. You might pump 10 billion litres of water, which is .02% of the volume of Mjøsa.
The problem is where to store it.<p>10 billion liters of water is 1,000 m^2 * 10m deep. There is no suitable location for that that is both elevated enough and near enough to Mjøsa to be financially viable.<p>Norway also existing hydro reservoirs with a capacity equivalent to around 6-8 months electricity supply, so it's not really a major need for Norway, anyway, but this is a fairly general problem: Finding suitable locations that are close enough to a water source, and provides a large enough potential reservoir is hard.
> You could use the ocean for the bottom level and an artificial reservoir for the top level. You're not going to noticeably affect ocean levels.<p>Then you have to deal with the problem of sea water corroding everything it touches.<p>> You might pump 10 billion litres of water, which is .02% of the volume of Mjøsa.<p>It's not the <i>amount</i> of water that you pump, it's the amount * the elevation delta. Where are you planning on getting the elevation delta from?<p>Neither of these challenges is technically insurmountable, but this is a field where capex + opex/KWH is <i>everything</i>.
> Where are you planning on getting the elevation delta from?<p>Elevation delta is not hard to find in Norway! A typical pumped storage facility uses 100m of delta; I imagine Norwegian ones would use more.<p>> but this is a field where capex + opex/KWH is everything.<p>And pumped storage is significantly cheaper for seasonal storage than any proposed alternatives.<p>The original post is efficient for heat storage, but converting low grade heat to electricity is not efficient.
> And pumped storage is significantly cheaper for seasonal storage than any proposed alternatives.<p>This is incorrect. There is currently not a single pumped hydro station that is suitable for seasonal storage. They're all designed to drain their upper reservoir in 4-16 hours.<p>It's the only thing that's half economical. Do the math: Even a modest power plant - 1 GW output - that can run for 1000 hours means you need a 1 TWh (even typing it feels ridiculous) storage reservoir. If you only have 100m of head, that's 3 cubic kilometers of water. That would mean building an artificial lake that immediately would be Norway's 6th largest body of fresh water, and draining it completely every winter.<p>And effectively, you'd have to build it twice - you also need a lower reservoir. Because there's nowhere to get 3 cubic kilometers of fresh water to fill it otherwise, and you really don't want to do pumped hydro with seawater.
For some applications, you don't actually convert the heat to electricity.<p>This sounds pretty cheap if it works out:<p><a href="https://austinvernon.site/blog/standardthermal.html" rel="nofollow">https://austinvernon.site/blog/standardthermal.html</a>
> A typical pumped storage facility uses 100m of delta<p>Most projects seek 200-600m. This map doesn't even consider pumped hydro <200m: <a href="https://maps.nrel.gov/psh" rel="nofollow">https://maps.nrel.gov/psh</a><p>> And pumped storage is significantly cheaper for seasonal storage than any proposed alternatives.<p>Based on what? Cost is particularly variable for pumped hydro. It can be one of the cheaper options when stars align. But you need 1) a suitable geography that minimizes the cost of damming or digging a resivoir with sufficient head 2) available for development without too much backlash 3) Near enough grid resources to minimize infrastructure and line losses. I'm surely leaving pieces out.<p>It <i>can</i> be cheap, but it has far more hoops to jump than alternatives like batteries, hot sand and other "storage-in-a-building" designs which can be built where needed and using fairly standard industrial construction.
True, but that disrupts ecosystems. Or so the argument against go building storage dams go.<p>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.
I think hydro storage is a lot less disruptive because you don't need as much space. Traditional hydro reservoirs have to last all season.
I 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.
Hydro doesn't work so well when things freeze over. Geothermal on the other hand...
> but it's fairly built out so stable non-fossil power needs to be nuclear,<p>Or just gas turbines running on decarbonized fuels. The backup for the "10 year winter" can be fossil fuels. It is such a minuscule problem that it does not matter in the slightest.<p>It is essentially the emergency reserve we are talking about, no point wasting tens of billions in subsidies per new built nuclear reactor.
That hydro is regularly turned off when it gets too cold.
Really? How do they turn it off? Where can I read about it?<p>I often pass the hydro bridge, so we have winters and whatnot - I didn't know they turn them off.<p>I can see hydro pumping power for all year long and being the top source of electricity in Latvia: <a href="https://www.ast.lv/en/electricity-market-review?year=2025&month=10" rel="nofollow">https://www.ast.lv/en/electricity-market-review?year=2025&mo...</a>
invest in saving/harvesting energy. Better than producing when solar is cheap as hell and you get no-solar-harvesting because of your location
I'm not ruling out Nuclear in general, but let's remember that:<p>* Energy can also be carried northward from other areas in the same country or neighboring countries, where there are more sunlight hours or more wind.<p>* Geothermal energy sources, e.g. <a href="https://www.rehva.eu/rehva-journal/chapter/geothermal-energy-use-in-the-nordic-countries" rel="nofollow">https://www.rehva.eu/rehva-journal/chapter/geothermal-energy...</a><p>* Increase in solar panel farm area<p>* Improvements in panel efficiency (which continue)<p>* Improvement in energy use efficiency<p>... in some combination, and with decent storage, might get even the Nordic countries to cover their needs.
1. The southernmost spot in Finland is too far north, and the scramble that happened in EU at the loss of Russian energy supplies made it crystal clear that we can not trust any other country to help in times of need.<p>2. We have no geothermal sources sufficient for production of electricity, it can only be used to slightly reduce primary energy use during winter, but it will raise electricity use during winter.<p>3. Helps not at all, because 0 times however large number you like is still 0.<p>4. Likewise.<p>5. Improvements in efficiency do not help you stay alive when it's -30°C.<p>The option up here really truly is "do we use fossil fuels, or do we use nuclear". Renewables do not help. They are nice to have, and it makes sense to build them because they complement the reduced output of nuclear in summertime, and because the lower cost/kWh can help some industry, but that's all.
The difference between baseline and peak electricity consumption in Finland is >2x. That's mostly driven by heating. Because renewables make electricity cheap on the average, utility companies invest in cheap heat storage systems such as sand batteries. They use electricity when it's cheap, store the heat, and distribute it when it's needed.<p>As for nuclear, the challenge is finding companies that are able and willing to build it. Areva and Rosatom both failed at the "able" part. And a power company (I think it was Fortum) recently stated that they would consider building new nuclear reactors with German electric prices but not with Finnish prices.<p>There is more to that than a power company asking for subsidies. Finland is a small country. Olkiluoto 3 alone generates >10% of the electricity. Newer reactors would likely be smaller but still ~10% of the total. Finnish power companies are too small to take risks like that on their own. They can't build new reactors at their own risk, in order to sell the power in the market. Before a reactor gets built, the power company needs long-term commitments from industrial users and utility companies to buy power for a guaranteed price. Such commitments would make sense for the buyer with German electricity prices but not with Finnish prices.
I think this is exactly right, and people are focusing on the wrong risk with nuclear. It's financial risk, not safety risk, that is the biggest burden for more nuclear.<p>Finland was very very wise and savvy to get a fixed price contract for Olkiluoto 3. The final cost was far far far above its price, and France ended up paying that price. I'm not sure if you'll see a builder go down that route any time soon again.
>The option up here really truly is "do we use fossil fuels, or do we use nuclear". Renewables do not help.<p>Hey now - renewables gave us electricity up here long before Einstein started thinking about atoms!<p>We are very few people here, 250MWh helps a lot, but if we have to chip in to build a nuclear plant we'll be broke before the project planning is done. ;-)
>2. We have no geothermal sources sufficient for production of electricity, it can only be used to slightly reduce primary energy use during winter, but it will raise electricity use during winter.<p>The project for properly deep geothermal for district heating in Espoo was not resounding success. And that is 6,4km deep hole in southern part of Finland. My understanding is that it somewhat worked. But not as good as expected.
> The southernmost spot in Finland is too far north, and the scramble that happened in EU at the loss of Russian energy supplies made it crystal clear that we can not trust any other country to help in times of need.<p>That's the failure of European union
Note that even if Central Europe did have sufficient energy for export it wouldn't really help during crisis. To get the energy to Finland it would need to either go thru the Baltic Sea via undersea cables or via Northern Sweden. We have seen that it's not necessarily good idea to rely on the former during the crisis as those lines can easily be cut, they have been multiple times in just past year or so by certain commercial ships "accidentally" dropping their anchors.<p>As for latter Sweden, doesn't currently have capacity for it and I don't think they have been very interested in increasing it, currently Finland often benefits from the fact that there isn't enough transport capacity between Southern and Northern Sweden electric grids so Finland gets some cheap electricity from there.
That's true, but it doesn't matter. It's not something we can change.
I don't think it's necessarily a failure of the EU for member states to prioritize stability and independence of their electrical grid.<p>Texas having their own grid is not a failure of American federalism.
> 3. Helps not at all, because 0 times however large number you like is still 0.<p>Show me your Monte Carlo simulation where wind (which is negatively correlated to solar) and 8 hours of battery storage are factored in, along with small amounts of gas peaking plants.
You don't even need to open up R or Pandas to understand that solar is not viable in the winter.<p>Here's the official meteorology insitutions sunshine data:
<a href="https://www.ilmatieteenlaitos.fi/1991-2020-auringonpaiste-ja-sateilytilastot" rel="nofollow">https://www.ilmatieteenlaitos.fi/1991-2020-auringonpaiste-ja...</a><p>Here's some solar production data over the seasons in visual form:
<a href="https://profilesolar.com/locations/Finland/Helsinki/" rel="nofollow">https://profilesolar.com/locations/Finland/Helsinki/</a><p>What is also important to know is during the winter is that while production <i>on average</i> shows numbers every day, in practice that production comes only during the few actually sunny days in December when the panels aren't covered in snow.<p>Go even a bit up north from Helsinki and unless you keep your panels clear of snow manually, you'll hardly make anything between Nov and April.<p>EDIT: Here's a reddit thread where someone shares real production data:
<a href="https://old.reddit.com/r/Finland/comments/1i6onkk/solar_energy_in_finland/" rel="nofollow">https://old.reddit.com/r/Finland/comments/1i6onkk/solar_ener...</a>
We have the problem of stable high-pressure polar air masses potentially parking over the country. Whenever that happens, we get 2 weeks of dead calm, coinciding with the coldest weather that occurs in the country. At the time of the year when there is no solar.
In case people want to play with a toy model: <a href="https://model.energy/" rel="nofollow">https://model.energy/</a>
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Right, the worst case scenario is cold temperatures, transmission problems (say days after a storm), lull, and nuclear and hydro power malfunction. However, it should be pointed out that winters are usually quite windy and there are only a few days per year you get very cold temperatures coupled with nearly no wind at all.
"there are only a few days per year you get very cold temperatures coupled with nearly no wind at all"<p>This is a terrible handwave. How many days per year, in the middle of winter, in a cold country, are you OK with having no power?
The system in the article works alongside gas and wood chips heating, so there are other options in place if the sand battery cannot be "charged".<p>FTA:<p>> The project will cut fossil-based emissions in the Vääksy district heating network by around 60% each year, by reducing natural gas use bu 80% and also decreasing wood chip consumption.
Not really, we're currently borderline. If OL3 goes down, and it's simultaneously cold over the nordics + northern germany and the baltics, and no wind, our industry will have to shutdown.
Why no power? The forests, hydro dams, heat plants and such that gave power long before wind became a thing are still there.
This would be an argument for widespread backup power, actually. If every residence had enough backup power to get through 24 hours, it would be far easier to deal with these relatively rare doldrums.
Please read the hn guidelines and reconsider your participation.
But "stable" isn't really want they want or need. They have a) cold, dark winters so they want more energy in the winter not a constant amount year round, b) hydro (89% of electricity in Norway!) that is already used as seasonal storage and can be varied to meet daily variation.<p>Cheap wind that produces more in winter is the obvious answer and indeed seems to be a focus of their build out.
> But "stable" isn't really want they want or need.<p>Yes, that is exactly what they need. They need stable energy over let's say a 1-2 week period. A windy week is often followed by a non-windy week. So if they can store the energy from the windy week and use it in the following week then they can rely on wind power as a stable energy source.
There'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.
It's even better than that. In addition to the factor of n from ratio of volume to surface area, there's also a factor of n from the increased thermal resistance of the mass of the storage volume (the temperature gradient from the surface to the center goes as 1/n). So, the thermal time constant of the object scales as n^2.<p>This very favorable scaling is why natural geothermal retains heat even though the input energy was delivered gradually over as much as millions of years.
I've always wondered why we don't build homes with a buried tank of water used as heat storage. In the summer it can be heated with solar thermal to around 90c, and in the winter heat can be drawn out and go through radiators or underfloor heating, with a mixer valve. You just need a few pumps and valves, not even a heat pump is needed.<p>If you assume a modern house with a heat load of 1800kWh per year (fairly standard for a new build medium sized home where I live, in Northern Europe) that means you'd need a tank roughly 50m3, or 10,000 gallons for Americans. In terms of insulation you'd need around 50cm of XPS foam, and it would be buried a meter below ground.<p>It's nothing terribly complicated in terms of construction or engineering. Of course you'd pay more upfront, but then your heating bills would be practically zero. In warmer climates it would be much simpler, you could probably get away without burying it.
This is essentially what a ground source heat pump system is. Except instead of a sealed water tank you just make a tall hole that fills with water and the sun will warm it for you during the summer automatically.<p>1800 kWh is <i>very</i> little. We use around 12000 kWh and our neighbours' new house uses around 8000 kWh annually and most of that is heating. I'm not sure how many houses can hit 1800.
You can also recharge your geothermal well or ground heat collection field by heating the outgoing thermal collection liquid with either cheap electricity (rooftop solar?) or direct solar heat collection. I think this will be a growing thing as the earliest mainstream ground source heat wells start to be a few decades old. Many of them are sized so that they don't fully recover during the summer, so the heat output slowly drops.
<i>A ground source heat pump (also geothermal heat pump) is a heating/cooling system for buildings that use a type of heat pump to transfer heat to or from the ground, taking advantage of the relative constancy of temperatures of the earth through the seasons.</i><p><a href="https://en.wikipedia.org/wiki/Ground_source_heat_pump" rel="nofollow">https://en.wikipedia.org/wiki/Ground_source_heat_pump</a>
Heath energy required != electricity requirement.<p>A modern house in Finland needs around 15-24kWh a year of <i>heat energy</i> if it's well insulated. On the higher end for big + northern houses, and less if you're smaller and further south.<p>Some get this energy by burning wood, others with heat pumps, and some with direct electricity.
I'm not sure if the 1800kWh is correct here. I'm guessing it's one of these two:<p>- You're talking about what heat pumps use in electricity. However, the system would store heat. If a heat pump uses 1 kWh to get 3 kWh of heat into the house, a heat based storage system needs to store the 3 kWh.<p>- You're confusing gas & electricity. 1800 m3 in gas would be about correct. However, that's about 9,5 kwh per m3 in heat.<p>There are interesting heat storage methods though, there is a long term basalt heat storage system in 'Ecodorp Boekel' in The Netherlands. It uses solar to heat during the summer and heats the homes with that in winter.<p>Due to size though, it only really works in 'collective' communities. The bigger the size, the more heat it can store per size.
I can't find the link now, but there was an episode of Grand Designs here in the UK (a show detailing private individuals developing interesting or unusual homes) where the owner was building a passively heated house based on an idea by his architect father.<p>The ground beneath the footprint of the house was insulated around the sides to a depth of about 2m, effectively extending the thermal mass of the house into the ground. After construction, it took about 2 years (IIRC) to warm to a stable level, but thereafter required little to no energy to stay at a comfortable temperature year round.
50m³ is huge. IMO that would be an engineering challenge that would probably impact the sability of the foundation if not done right.<p>Ground source heat pumps are expensive because of the buried piping, I imagine this would be even more costly.
Something like that was attempted south of Calgary, in Canada: <a href="https://en.wikipedia.org/wiki/Drake_Landing_Solar_Community" rel="nofollow">https://en.wikipedia.org/wiki/Drake_Landing_Solar_Community</a>
Its kind of done. Active heating systems often have the intake air go through the foundation so it heats up in summer and cools down in winter reducing both heating and cooling costs.
Billions, mostly.
Just as important here: The higher the temperature of the storage medium, the higher the fundamental limit to how much electric energy you can recover.<p>Put differently: If you used the same amount of energy to heat one bucket of sand by 200C (A) or two bucket of sands by 100C (B), you would be able to recover more electric energy from case A because of the fundamental Carnot Limit.
This is why sand is a good storage medium (as opposed to e.g. water), and why some solar power systems work with molten salts. Also why steam-based power plants need to operate at high pressure to be able to obtain high-temperature steam.
Yes and a freezer that is only a bit larger, taller or deeper has a lot more liters of storage. Not just because it's in 3D but also because a smaller freezer still needs big sides. So, a lot more liters but only a tiny bit more energy consumption.<p>ps: living in an area with a high price per square meter goes against this strategy unless you manage to share a freezer
Yeah but if you transfer the energy as heat then you will end up with elongated structures (pipes).
You speak theoretically but metropolitan areas in these countries all have those pipes in place and in use for the better part of a century.<p>Using heat for heating has many redeeming qualities. Heat is high entropy and it is not a good idea to "waste" low entropy energy to create high entropy energy. Many industrial processes run on heat and waste heat is generated everywhere. The systems are also cheap to run once in place.
That's a real issue, but this is for a district heating system which already exists and already faces this issue. And yet the district heating system is presumably practical.<p>Changing to a different central source of heating (i.e. storage) seems orthogonal.
Is that a problem? Pipes are not technically complicated. Is there something else I'm missing?
Larger storage structures are easier to (thermally) insulate. Because geometry.<p>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.
Existing district heating systems can be large.<p>I live in Denmark the powerplant that heats my home is about 30km away. There are old powerplants in between that can be powered in an emergency.<p>Yes, building district heating systems that large is difficult and expensive, it wasn't built yesterday, more like 50 years of policies.
I can't help but wonder how the efficiency compares to generating electricity, running that over wires, and having that run heat pumps.<p>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.<p>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.
> heat pumps themselves are much more efficient.<p>For electricity-to-heat conversion, heap pumps are indeed much more efficient relative to resistive heating, yes. About 4 times more efficient.<p>In absolute terms, though - that is still only 50% of "Carnot cycle" efficiency.<p><a href="https://en.wikipedia.org/wiki/Coefficient_of_performance" rel="nofollow">https://en.wikipedia.org/wiki/Coefficient_of_performance</a><p>Similarly, heat-to-electricity conversion is about 50% efficient in best case:<p><a href="https://en.wikipedia.org/wiki/Thermal_efficiency" rel="nofollow">https://en.wikipedia.org/wiki/Thermal_efficiency</a><p>So, in your scenario (heat->electricity conversion, then transmission, then electricity->heat conversion), overall efficiency is going to be 50% * 50% = 25%, assuming no transmission losses and state-of-art conversion on both ends.<p>25% efficiency (a.k.a. 75% losses) is pretty generous budget to work with. I guess one can cover a small town or a city's district with heat pipes and come on top in terms of efficiency.
We've got lots of heating districts around the world to use as examples. They only make sense in really dense areas. The thermal losses and expense of maintaining them make them economically impractical for most areas other than a few core districts in urban centers... Unless you have an excess of energy that you can't sell on the grid.
I don't understand, what am I missing? The heat pump increases efficiency by having COP 2-4 right? Assuming air to air and being in, say, Denmark.<p>Heat (above 100C, say, burning garbage) to electricity: 50% (theoretical best case)<p>Electricity to heat (around 40C): 200%-400%<p>Net win?<p>The surplus energy comes from air or ground temperatures..<p>Yes you cannot heat back to the temperature you started with but for underfloor heating 40C is plenty. And you can get COP 2 up to shower water of 60C as well.
It can be anything between easy and impossible depending on the temperature difference. 200 C steam is easy with a commercially available turbine, but 50 C is really hard. There are things like Sterling engines that can capture waste heat but they've never really been commercially viable.<p>There's no way around it: We have to respect entropy.
If the heat is stored at high temperature, but the demand (for heating buildings, say) is at lower temperature, it could make sense to generate power, then use that power to drive heat pumps. You could end up with more useful heat energy than you started with, possibly even if you didn't use the waste heat from the initial power generation cycle.<p>Alternately, if you are going to deliver the heat at low temperature to a district heating system, you might as use a topping cycle to extract some of the stored energy as work and use the waste heat, rather than taking the second law loss of just directly downgrading the high temperature heat to lower temperature.<p>High temperature storage increases the energy stored per unit of storage mass. If the heating is resistive, you might as well store at as high a temperature as is practical.<p>Gas-fired heat pumps have been investigated for heating buildings; they'd have a COP > 1.<p>I am interested if there are any cheap small scale external combustion engines available (steam? stirling? ORC?)
I think the big cost difference is the geothermal generators to convert the heat back into electricity. More of a cost issue versus efficiency.
Pipes are competing with wires, which are <i>much</i> less technically complicated than pipes.
From the article:<p>> [250MWh] held in a container 14m high and 15m wide<p>According to Gemini 3.0 Pro, lifepo4 is 1.5-3.5x more dense than this, which isn't bad. 250MWh is a lot of capacity for such a small land footprint. At 2MW it can power ~2000 homes for ~5 days while taking up the land footprint of ~1 home.<p>What's the price? And how does the price scale with capacity?
I 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.<p>Peltier modules can be used to generate electricity, but they are crazy inefficient.<p>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.<p>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.<p>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.
The 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.<p>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.
Non-steam turbines have been operated (e.g. <a href="https://en.wikipedia.org/wiki/Mercury_vapour_turbine" rel="nofollow">https://en.wikipedia.org/wiki/Mercury_vapour_turbine</a>), but… steam is just so much easier to work with.
You missed thermoelectric generators that uses the Seebeck effect to generate a current between two temperature differentials. It's terribly inefficient, unfortunately.
> An efficient steam turbine is largely inaccessible to hobbiests and I am scared of steam/pressure.<p>Thermal electricity generation really benefits from scale and extremes. The Carnot efficiency is proportional to the temperature differential between hot and cold. Even so-called "low quality" heat from a standard nuclear rector design is far hotter than anybody should deal with at home and it only gets ~1/3 efficiency. And dealing with small turbines is really inefficient too.<p>This is where batteries and solar really shine. They scale so well, and are extremely economical and electrically efficient.<p>Heat storage works well when you get beyond the scale of individual homes, but it's hard to make it work. I'd love to see something related to heat pumps in the future for homes, but district heating, such as could be accomplished by converting natural gas systems to heat delivery, are probably required for it to make sense.
Yeah, sadly, it seems almost impossible to get anything higher than 30% efficiency (theoretically with a Stirling engine, if you can find one, haha) out of a thermal battery without extreme pressures and temperatures.<p>Back-of-the-napkin math felt promising. A 1kg block of sand heated to 500 degrees Celsius should contain about 100Wh of electricity. Scaling that capacity up is easy, as it's just about adding sand or temperature (+ an effective method of transporting heat across the sand - maybe sand + used motor oil?).<p>Assuming 80% efficiency, tariff arbitrage (buy electricity during off-peak hours and use it during high-price hours) would pay off very quickly. In my area (Australia) it would be a matter of months - but the low real-world efficiency and lack of parts make it impossible.<p>It could work for heating during winter, though perhaps an AC/heatpump with the condenser a couple metres underground would be better value for money.
Heat storage <i>can</i> work for individual homes on the shorter scale. If you heat your home with in-floor heating (lower temperature requirements) you can have ~1-2m3 buffer tank that you heat up during the night and then use the stored heat during the day to heat your home. Works very well.
This project is for district heating, not producing electricity.<p>In general it is true that low-grade heat is difficult to convert to electricity, and there isn't any existing mass-market device that does it. You'll have to make your own, which involves learning to machine and responding to your perfectly reasonable fear of steam and pressure with proven safety measures.
In the articles case the end use of energy is household heating, so there is no need to convert back to electricity. The whole beauty of thermal energy storage that the end use of energy in many use cases is.. heat: heating buildings, cooking, industrial heating (from food processing to iron smelting), producing steam, etc.
Every couple of years I look around to see if anyone is selling sterling cycle engines in the 5-10 hp range, I always find a couple neat projects but nowhere can you just buy an engine.<p>I assume that because there is no current market for small sterling generators nobody wants invest in tooling to make one and because there are no small sterling generators there is no market for them.
LFP is so cheap that small-scale thermal battery makes not sense for electricity generation. Even in big scale (like OP) it mostly makes sense for heat, e.g. district heating systems, industry process heat, etc.
<a href="https://en.wikipedia.org/wiki/Thermoelectric_generator" rel="nofollow">https://en.wikipedia.org/wiki/Thermoelectric_generator</a><p>Seebeck generator, generally. Peltier goes the opposite way. But basically the same thing.
If you need to use heating in a cold climate, you could use your stored energy to heat the radiator of a heat pump, which would then be drastically more efficient than using normal air on the radiator.<p>There's a video of people doing this on YouTube. They use the ground as their heat source. <a href="https://youtu.be/s-41UF02vrU" rel="nofollow">https://youtu.be/s-41UF02vrU</a>
This is great news! Congrats for this fantastic progress.
Finland's current energy equation according to Google Gemini:<p><pre><code> Is Finland importing household garbage from Italy and why?
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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.<p><pre><code> Why you call it "processed"? It is raw garbage in huge mounds smelling bad and harboring flies and rats?
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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.<p><pre><code> Lets try again. Why the "processed" mound of garbage from Italy smells bad and houses flies and rats?
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Gemini: ... Sometimes ....<p><pre><code> This is not "sometimes", it makes living near Loviisa harbour impossible.
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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.<p>===<p>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.<p>The situation is desperate; any shit from anywhere at any cost is better than using local renewable biomass, such as peat.<p>Finland has enormous amounts of peat, which is worth more than Norway's oil reserves.
The comment is slightly incoherent in it's argumentation, but factually correct.<p>I think the point is the energy policies in some of the nordics are as arbitrary and politics driven as anywhere.<p>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.
Pedophiles were insulted, I am sorry. Correct English expression is maybe "Baby Lovers"? I dont know.
Peat grows at about 1 mm per year, if it regrows at all at the location where you did the extraction.
Why 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.<p>Why did we go to the moon when we have perfectly good vacuum chambers here at home.<p>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.<p>"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"
In a cold climate, I would expect burying it to use the ground as a natural insulator. Why was an above ground design chosen?<p>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?
The 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).<p>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.
The cost is a function of the size and mass. So, more heat capacity and less mass means lower cost per mwh.<p>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.
><i>The use of sand, presumably heated to a much higher temperature than the boiling point of water</i><p>600°C according to their website.
Those of us in the UK will recognise this as a giant "Economy 7 Night storage heater".
I 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.
Interesting. 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 ?
Wind 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.<p>Heat is transferred using disctrict heating networks where 65-120 C water is circulated.
It's a heat battery for district heating. Could be other sources than electricity, e.g. municipal garbage incineration plant.
No, these generally use excess power during the night and windy days to store heat.<p>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.
Most likely <i>not</i> 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.<p>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%).<p>What might be plentiful is wind, especially during the nights.
See my other comment about Nordic power balancing.
Natural gas and wood chips,<p>> <i>"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."</i><p><a href="https://www.pv-magazine.com/2025/11/25/finlands-polar-night-to-build-250-mwh-sand-battery-for-district-heating-provider/" rel="nofollow">https://www.pv-magazine.com/2025/11/25/finlands-polar-night-...</a>
Those are the energy sources they're replacing with this tech - according to <<a href="https://reneweconomy.com.au/new-worlds-largest-sand-battery-to-double-the-size-of-current-record-holder/" rel="nofollow">https://reneweconomy.com.au/new-worlds-largest-sand-battery-...</a>> 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)
These 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.<p>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.<p><a href="https://www.orcasciences.com/articles/standard-thermal" rel="nofollow">https://www.orcasciences.com/articles/standard-thermal</a>
Doesn'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.<p>Also the capex from sand battery goes to (mostly) local construction, while when buying chemical batteries all the money goes to china.
But thermal storage doesn’t wear out, unlike batteries, right? So less future maintenance. Plus there is no danger of battery puncture.<p>More directly this is a very cold area. Enough it might effect battery storage enough to be a real problem.
A website called energy-storage dot news should not be mixing up energy and power
I 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..."<p>and how a news outlet about energy could get such a fundamental unit wrong.<p>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.<p>"...It follows Polar Night Energy completing and putting a 1MW/100MWh Sand Battery TES project into commercial operations this summer..."
It'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:<p>> "This latest project will use locally available natural sand, held in a container 14m high and 15m wide."
would someone give an ELI5 on how a sand battery works? Is it just purely thermal mass, just with tons of sand?
You 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.
There's pipework for circulating air inside it when they want to charge/discharge it, but yes, essentially it's mostly tons of sand.<p>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.
I like how sand batteries are the equivalent of sleeping on the ashes of your fire
I never see sand battery before<p>between this and salt battery which one is the future???
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EU is going to have to either<p>- embrace nuclear<p>- 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.<p>We'll see what they choose :D
EU 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.<p>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.<p>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.
Here's your modeling site:<p><a href="https://model.energy/" rel="nofollow">https://model.energy/</a><p>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.
This is really interesting.<p>I put some numbers into this, and the required power for long term storage is significantly lower than I'd have expected.<p>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).<p>Overprovisioning (wind/solar) is suprisingly high, with 180GW of wind and 440GW of solar. Currently installed capacity for those is about 30% of that.<p>Short-term storage capacity is a really big gap though (the model suggests 750GWh, and currently there's <30GWh installed).<p>In conclusion: Under pessimistic simplifications, Germany is at about 30% progress toward fully renewable electricity (but battery capacity is lagging behind).<p>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...
The amount of long term storage (and the duration) depends on the balance between wind and PV.<p>If wind and PV have similar levelized cost of energy (LCoE), then the solution will use the lack of correlation between the two to avoid much storage. In this case, long term storage is over period of the variability of wind, which might be weeks.<p>But if PV is significantly cheaper than wind -- and this is where trends are going -- then long term storage becomes more for seasonal leveling, at least at high latitudes.<p>There's still a large place for short term storage, and economics is still strongly affected by the cost of that storage. So it's great news batteries have become so cheap to produce.
Why do you say "embrace nuclear" when the EU has substantial existing and planned nuclear plants? (Current gen is something like 24% nuclear in EU, 20% in wider Europe, 18% USA, 4.4% China)<p>And anyway, alongside that world leading nuclear already in existence why wouldn't they just install lots of cheap solar and wind, and heat pumps and EVs and reduce their imports of energy from their current high levels (about .6 Trillion euros in 2022, down to .35 in 2024 though that seems mostly a change in price, volume has declined only slightly)
The EU has plenty of solar and wind resources.
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