Finland inaugurates world’s largest 1 MW/100 MWh sand battery

Finland has inaugurated the world’s largest sand battery, a 1 MW/100 MWh thermal storage system developed by Polar Night Energy. The unit is already exceeding efficiency targets.

Finland has inaugurated the world’s largest sand battery this week, a 1 MW/100 MWh thermal storage system developed by Polar Night Energy.

The industrial-scale unit in Pornainen began operating in June after district heating company Loviisan Lämpö commissioned it. The company now uses the sand battery as the main production facility in its district heating network.

Polar Night Energy said the battery has met expectations in its first months and exceeded guaranteed efficiency targets. It has replaced the area’s old woodchip plant all summer.

A sand battery stores clean electricity as heat in sand or other solid materials. The Pornainen unit stands nearly 13 meters tall and 15 meters wide, delivers 1 MW of thermal power, offers 100 MWh of storage, and contains roughly 2,000 tons of crushed soapstone.

Polar Night Energy said the battery can participate in electricity reserve markets, charging according to electricity prices and Fingrid’s reserve market signals. Its storage capacity allows consumption to be optimized over days or weeks and helps balance the grid.

Finnish Minister of the Environment Sari Multala said thermal storage improves energy system flexibility and reduces industrial emissions.

“Energy storage plays an important role in the energy transition, where combustion-based production is phased out and society moves toward carbon neutrality,” Multala said. “The Pornainen sand battery is a great example of how the clean transition can be advanced through the electrification of district heating networks.”

Polar Night Energy is negotiating several large-scale thermal storage projects for district heating, hot air, and process steam production. Chief Operating Officer Liisa Naskali said industrial applications are promising, especially where heat above 100 C is required – beyond what electric boilers and heat pumps can provide.

The company also plans to begin constructing a pilot project in the coming weeks to test its power-to-heat-to-power sand battery technology.