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.

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.

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

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)?

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.

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.

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

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?