Finland using a "thermal battery" is used for heating

Thanks to a new thermal energy storage system, when residents in this small town north of Helsinki need hot water, it comes from a giant tank of super hot sand.

Excerpt: "A small town in Finland is experimenting with a new type of infrastructure: the world’s largest sand battery.

The battery—a 42-foot-tall, nearly 50-foot-wide silo filled with 2,000 tons of crushed stone—sits on the edge of a parking lot. When there’s extra renewable electricity on the grid and power is cheap, the system uses electricity to heat up the crushed stone. That heat is stored in the battery until nearby buildings need to use it.

The basic approach is simple. “We just heat air and [circulate it] through sand,” says Liisa Naskali, COO of Polar Night Energy, the Finnish startup that designed the technology. Sand, or other material crushed into sand-size particles, has the ability to store heat for weeks. Unlike some other batteries, the system doesn’t rely on chemicals, doesn’t degrade, and won’t catch on fire."