Finland’s radical answer to renewable energy’s biggest headache: The world’s largest sand battery

That's so cool! It even sounds cool: sand battery.

For more on strange batteries, Half As Interesting did a really cool video on different ways we do long-term energy storage.

As long as you can expect some periods of very cheap energy before its cold so you can warm it up again, seems like a decent idea actually.

How do they heat it, ideally would be using heat pumps.

I honestly thought it would be bigger. Having said that, we (as in the municipality i work for) currently have 40-60 MWh sand batteries in production. The first, small and hot, one is currently charging to go into production when it gets colder. The bigger and colder battery is slated to start charging the next season.

“And you can store it for long periods, not just two hours or four hours like lithium-ion batteries, but potentially for days and maybe even weeks.”

I'm guessing here, but "for days and maybe even weeks" must be because the battery is above ground? With good insulation seasonal storage is very much in the cards.

A day care in another Swedish municipality use about 1/5 of the "normal" energy for heating thanks to a sand battery. As in 15-18 kwh/m2/year as opposed to 70 kwh/m2/year as is the current upper limit for new buildings in Sweden.