Heat batteries are a game changer for decarbonising heat.

Polar Night Energy and Lahti Energia Oy have partnered to construct what is expected to become the world’s largest sand-based thermal energy storage system, to be built in Vääksy, Finland.

www.environmentenergyleader.com/stories/worlds-largest-sand-battery-to-supply-district-heat-in-finland,120570

April 10, 2026 - 07:23 UTC

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Haven’t they used salt for a similar heat storage purpose?
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I think that molten salt is used in solar collectors but the economics of solar PV have now exceeded that of solar collectors.
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Fourth law of thermodynamics ... Things get worse under pressure.
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I was wondering why water is not used for heat storage rather than sand since water has a much higher specific heat.
When the equipment and labor cost of using water is calculated,sand is cheaper. Air handling is cheaper than water handling.
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Elsewhere in this thread I was reading about a company doing just that, with massive pressurized (to raise the water to higher temps than normally possible) underground chambers filled with 140c water.

Though as an observer here I do agree that water doesn’t seem to make a ton of sense.
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There are storage systems with water. It's 2 different approaches, each with pros and cons. The advantage of sand is you can heat it up to 500°C. This means more energy per volume, but also you could turn this heat back to elec with a reasonable efficiency (because higher Carnot limit)
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Nope sand has a higher storage capacity at 500 degrees than water ~100 degrees.
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Maybe because sand can be heated to 500C+ and is easier to heat to that temperature
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why use sand when you could just use the subsoil on the site? why make a big tank when you could just leave it in the ground?
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Presumably because, in order to retain the heat the tank has to be well insulated.
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Any evidence on how this would work specifically? How would you be able to store heat at hundreds of degrees in the subsoil?
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Colder countries need to plan new housing complexes and estates with district heating to take full advantage of this. I expect it will be more expensive to store heat or heatpumps on a per household basis if it isn't feasible to retrofit housing dependant on piped natural gas.
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In addition to sand batteries, Finnish utilities are also building the world's largest #CavernThermalEnergyStorage in Vantaa (1,1 million m³)
www.vantaanenergia.fi/en/about-us/projects/varanto-the-cavern-thermal-energy-storage/
and the world's largest #PitThermalEnergyStorage in Hyvinkää (380.000 m³)
hlv.fi/lampovarastohanke/
#SectorCoupling
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TES? aka-tosh been dragon already, sands of time without the hourglass keep the energy ready, bean counters love the hot rocks bc they save fetti, now they're making that gritty bread like an ancient Egyptian or a person whetting
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Kind of worries me given what I hear about sand issues in construction
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I have no idea but it just might be that a non construction grade smooth sand can be used as a heat sink.
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What is wrong with green electric heating?!
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Nothing wrong, but doesn’t work necessarily in Finland.

Finnish electricity market depends a lot on renewables, mostly wind. There is little wind when heating is most needed (cold winter days), which leads to price hikes. Solar is no fix to this either. Storing heat like this will even the highs.
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@mayorgallego.bsky.social If youre gonna welcome #datacenters to #Phoenix, this is something to explore. We have no shortage of sand and solar but we do have limited water, and we are already too hot thanks to our concrete, asphalt, and fossil fuel cars jammed up on freeways 6 hours or more per day
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When I was a child I played around a construction site. Dug into a pile of soil they had dug out. Found snow in there, in June.

So why wouldn't it work the other way around.
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please do u know the COP of this System and how it’s heating and on which way the heat becomes to electricity again ⚡️
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It doesn't, the heat is transferred to the heating system as heat usually with hot water as the medium.
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See also Caldera here in the UK.
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Been watching this development for a few years Britain needs thease to replace gas powered power stations. We generate a lot of excess wind power so store it and use it when we need it.
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I have seen some criticism of this idea based on the amount of heat lost to the environment without pretty insane insulation. Perhaps they have invented that.
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Brilliant idea 💡
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It's really cool to see the energy transition developing before our eyes, notwithstanding the interference by reptilian profiteers.
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To think there's probably nothing here that couldn't have been done 50 years ago already.

Such waste.
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A key part of the Pornainen Sand Battery’s profitability lies in optimizing its operation according to electricity prices and Finland’s grid operator Fingrid’s reserve markets. In doing so, the Sand Battery supports power grid stability, an essential enabler of the rapid growth of renewable energy.
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