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.

> That's for 5000 people.

And it's quite compact.

> And only covers heat.

Is that not useful?

Don't get me wrong, this is cool. We just have some stricter requirements on a country/state/union level that while this might help with parts, I don't see how it can easily scale up and generalize

It scales up just the way that siloes on farms scale up ... you build more of them.

And the Finns put a priority on staying warm. For normal electrical generation, they largely use wind with a growing solar fraction.

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

going from burning fuel 12 months of the year to 3 is still a 75% cut in fuel costs and emissions

Finland only started building solar recently. Wind is still more cost-effective, if you only consider the cost of generation. But there is almost too much installed wind capacity. If you also consider the value of the generated energy, solar gets ahead, as it correlates less with existing generation.

In any case, Finland does not really use fossil fuels for electricity generation anymore. There is some cogeneration, where heat is the primary output, and reserve power plants that are only used in exceptional situations. Electricity is largely a solved problem, but it's proving harder to get rid of fossil fuels in heating and transportation.

That doesn't really make sense, you need the ability for significant overproduction before you start thinking about storage. The other way around is just wasting money. We are just starting to get there, but still have significant fossil fuels that we can replace even by just building out solar more and just having more over production.

Not necessarily. A large component for solar+storage is using the storage to offset the time that the energy is available. It's not just storing for overproduction

For instance, most places will have peak energy usage in the evening, when everyone gets home from work, starts the laundry, turns up the thermostat and makes dinner and such, kind of all at the same time

If you can store the solar energy at noon and use it at 6pm when everyone has come home from work and started making dinner, then you can prevent a demand peak from ramping up fossil fuel plant

So you aren't necessarily just aiming to store the overproduction, you're using the stored solar when it's more useful

Usually there's either sun or wind. Last year 57% of Finland's electricity generation was from renewables, the rest being largely nuclear, and the electricity costs were among lowest in Europe.

Until battery tech gets (and maybe even after) it's a good idea to build some nuclear too.

The places that don't have much sun instead tend to have much wind and hydro.