Finland:

> The net result: Pornainen fulfilled all of its municipal climate targets with a single installation. Oil use dropped 100 percent, emissions fell 70 percent, and woodchip combustion was cut by 60 percent. According to the Mayor of the Municipality of Pornainen, Antti Kuusela, the municipality now heats all its public buildings, including a new sports arena opening in September 2026, entirely through this district heating network.

https://interestingengineering.com/energy/sand-battery-polar...

That's for 5000 people. And only covers heat. Happy if it can scale and move from prototype to long-term deployment at a reasonable cost, serving heavy industry in manufacturing.

They are buying electricity and storing it as heat and time-arbitrage it to when the heat is needed, they make no mention of the electric power source. In any case, during the depth of winter, when it's needed most, they're still burning carbon. Previous paragraph to your quote:

>During the coldest, most expensive stretch, the wood chip boiler became the primary unit, and the sand battery supplemented it.

Remarkably: heat is pointed to as "wasted energy" when doing EROEI analysis and discounted, this is done to strengthen the case for Solar vs Gas.

Finland's energy mix is ~6% solar [1]... maybe it's not a larger portion of the grid supply because Finns realize it doesn't work in the winter?

[1] https://www.iea.org/countries/finland/energy-mix