Finland’s Sand Battery: Storing Green Energy Beneath the Surface
In a world racing to decarbonize, one of the greatest challenges remains unsolved: how to store green energy for when the sun isn’t shining and the wind isn’t blowing. While lithium-ion batteries have long dominated the energy storage conversation, Finland is quietly pioneering a radically different—and surprisingly simple—solution: sand.
In the town of Kankaanpää, western Finland, engineers have built the world’s first commercial-scale sand battery, using low-cost, abundant sand to store excess renewable energy as heat. Developed by a Finnish startup called Polar Night Energy, this innovative system offers a glimpse of the future—one where renewable energy is not just produced cleanly but stored sustainably.
“It’s simple, low-tech, and extremely efficient,” says Markku Ylönen, co-founder of Polar Night Energy. “We’re proving that sand can do what lithium can’t—store large amounts of energy affordably and without rare materials.”
At the heart of the system is a 7-meter-tall steel silo filled with 100 tons of builder’s sand, connected to a district heating network. When wind or solar farms generate surplus electricity—often at night or during low-demand periods—this clean energy powers resistive heating elements embedded in the sand, raising its temperature to around 500–600°C (932–1,112°F).
