[myrmidon]

> Finland is still 25% oil for electric generation [1] (and almost 40% fossil fuel). That means a lot of the electricity to heat the sand still comes from oil.

This is not a valid conclusion. Battery projects like this are gonna charge/heat up when the electricity price is low, electricity price is low when supply/demand ratio is high and this often happens when renewable electricity is most available and makes up a disproportionate share of the electricity mix.

Edit: Your graph is not what you say it is, this shows primary energy (i.e. includes fuel/heating/...), not "electric generation". Electricity in Finland is mostly nuclear, wind, hydro and certainly not "40% fossil fuel".

[dguest]

I think the primary energy does include electric generation, but you're right, I posted the wrong chart. The correct one is here:

https://ourworldindata.org/grapher/electricity-prod-source-s...

and it backs up your point. Sorry to any Fins I might have offended with my lazy post.