Finland warms up the world's largest sand battery, the economics look appealing

https://techcrunch.com/2025/06/16/finland-warms-up-the-worlds-largest-sand-battery-and-the-economics-look-appealing/

by pseudolus • 1 year ago

104 26 1 year ago

  Polar Night didn’t disclose the project’s cost, though the raw materials are cheap and the structure itself isn’t particularly complex. A much smaller prototype built a few years ago cost around $25 per kilowatt-hour of storage, the company estimated at the time. It’s likely the new version is cheaper. Lithium-ion batteries cost around $115 per kilowatt-hour.

“Economics look appealing”, but does not include costs.

senectus1• 1 year ago

yeah its not doing the project any favors is it.

oliwarner• 1 year ago

They've only built two of these things in production. I think it's okay to use forecast costs when it's this early. I assume they'll get better at this, production gets cheaper and the bulk of the material will actually be a logistics cost rather than materials, so putting sticker prices on these might not translate well.

But the "smaller prototype" is 8MWh. Their estimate of $25/kWh would make that $200k, and this 100MWh unit should scale to $2.5M but there have already received many times that in funding. Who knows.

passwordoops• 1 year ago

I love the idea behind heat batteries but... "Polar Night didn’t disclose the project’s cost"

So we're using Trust Me Bro accounting everywhere now?

VladVladikoff• 1 year ago

Interesting concept. Sort of a terribly written article. Things the author should have talked about: 1) comparison between life expectancy of a lithium ion battery vs a sand battery

2) environmental impact of lithium ion battery waste, vs sand battery.

3) ethics of lithium mining.

4) how lithium ion batteries perform poorly at colder temperatures (eg Finland)

There are a lot of strong arguments for these batteries the author seemed to just skip over, and instead focused on costs, which they don’t know the answer to.

metalrain2• 1 year ago

I don't think lithium ion is even the right comparison in this case. This could more comparable in spirit, although 900 times bigger in capacity and not yet finished. https://www.vantaanenergia.fi/en/about-us/projects/varanto-t...

If you try gauge the price from that cavern storage (estimated 200 million euros) then lets say it has some economies of scale, maybe this sand battery costs like 500k-1M euros.

If you just heat the storage on cheap hours and output at high prices. You could in theory cycle (24*365/2) hours at 1 MW so 4,4 GWh of energy per year. So how could be the project profitable?

In 10 year period with full utilization price differential would need to be 22.8 €/MWh to break even with 1M investment, then add operating costs, loan interest, etc. With more realistic utilization it would need to even higher.

Maybe you amortize costs over 20, 30 years. But its's even more uncertain what cost of electricity will be. I think it only makes sense if this storage allows them to electrify heat production replacing much more expensive current production.

lrasinen2• 1 year ago

22.8 €/MWh is just 2.28 c/kWh and that's a very low bar to clear.

Just yesterday we had 6 hours of negative prices, followed shortly after by one hour at 2.66 c/kWh and four more over 3 c. Friday had swings from 0.4 c to 13 c.

(All prices with VAT included)

And this is in summer when energy consumption is low, the swings will intensify when the heating season starts.

foxglacier• 1 year ago

That and the downsides to the sand battery. We don't need more biased new stories trying to promote everything as miraculously pure-good. Environmental concerns hardly matter for utility energy generation because if it's not cheaper, it will will either completely fail or be a tax on everyone if the government mandates it.

The obvious problem is it can only really be used for heating, not electricity. But heating is still a fine use when available.

bodiekane• 1 year ago

Surely the environmental concerns are the larger "tax on everyone".

Fossil fuels appear cheap specifically because the benefits accumulate to the corporation extracting and selling them, while a substantial portion of the costs get unevenly distributed to random people who's homes get destroyed by hurricanes or wildfires as well as everyone having to run their air conditioners more.

standardUser2• 1 year ago

This technology has been big in Australia for a while. I always wondered why it didn't catch on, given the relative rarity and expense of more 'advanced' battery materials. Now that lithium-ion seems to be taking over I wonder if these salt/sand thermal batteries will have a role.

Quarrel• 1 year ago

is it actually "big" in Aus?

I know MGA Thermal have a demo project that the gov funded, but is there anything in commercial use?

standardUser2• 1 year ago

Big in terms of development, not commercial use.

chii2• 1 year ago

afaict, the thermal battery isn't for storing electricity but heat - something that's not really "needed" in australia, as there's no heating utility transport there. Turning this heat back into electricity is inefficient (not sure if that was tried tbh).

It would be good if this worked out at scale of course; i do like that this type of battery can be made with cheaper materials. It makes it so that utilities/gov't can make use of large economies of scale, and have the benefits of renewables benefit everyone, not just people able to afford a solar/lithium battery pack at their property.

stubish2• 1 year ago

I would like a residential scale one, assuming it is more efficient than using solar generation to charge a regular battery to power a reverse cycle air conditioner at night. I guess it isn't more efficient?

magicalhippo2• 1 year ago

This isn't really a battery. It's storing heat, to be used as-is for the towns centralized heating system. Thus you lose a lot less on the usage-side compared to if it was truly used as a battery, ie to generate electricity.

Here the "battery" is "charged" using electricity as input, however the electricity in Finland comes mostly from nuclear, wind or hydro[1], so should be able to utilize the renewable peaks well.

But yeah, I'd be surprised if this system would be as cost-effective if you didn't already have a centralized heating system to plug this into.

[1] https://stat.fi/en/statistics/salatuo

someothherguyy2• 1 year ago

"It is true that we have been trying to avoid the word battery, since technically speaking it is not what we have. Anyhow, the word caught fire, and was a big part of the media success, and it probably was McGrath’s invention. Of course if we were to generate electricity from the heat, it would at least act like a battery does: taking in electricity and giving back electricity."

(2022) https://www.treehugger.com/viral-sand-battery-isnt-what-it-s...

jfengel• 1 year ago

The word "battery" is often misused anyway. A "battery" is a collection of things, from the military use as a coordinated artillery group. A single "battery" is really a cell.

The word has been used that way for a long time, so I'm not gonna stamp on my dictionary and insist we look at the etymology. But it does show how the word's usage has shifted, and a continued shift to call this thing a "heat battery" seems comprehensible.

magicalhippo2• 1 year ago

Goid point. I do like "heat battery".

My complaint was more that just "battery" implies storing electricity directly in common parlance these days, and the fact that the heat output is used directly is quite significant.

Had the headline called it a heat battery I would have had no complaints.

someothherguyy2• 1 year ago

https://news.ycombinator.com/item?id=31618476

ZeroGravitas• 1 year ago

This has stiff competition from standard lithium or sodium batteries combined with giant industrial high temp heat pumps and distributed low temp heat pumps.

I can't quite see the niche that's left, and from their talk about possibly generating electricity from the stored heat, it seems they can't either.

Maybe as a buffer for continual industrial processes that are above heat pump reachable temps (which means above 200C these days)?

metalman• 1 year ago

This idea has been around for a while, and scales both ways.... I know house where where 40 tons of crushed rock were added to a new basement enclosure under a new large south facing sun room, that has fans and a differential controller to pump excess heat into the rock, was built in the 1980's here in Nova Scotia, the house only needs suplimental heat for comfort in the form of a small wood stove.

Finland warms up the world's largest sand battery, the economics look appealing

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