• Finland’s new sand battery in Pornainen stores 100 MWh of heat, cutting heating emissions by nearly 70%.
  • The system uses recycled soapstone to provide up to a week of winter heating, eliminating oil and reducing wood chip use by 60%.
  • Cheap, scalable, and efficient, the technology points to a cleaner, more affordable future for district heating.

Finland has launched the world’s largest sand-based thermal battery in the town of Pornainen, marking a major leap in affordable, sustainable energy storage.

Developed by Polar Night Energy, this industrial-scale installation uses 2,000 tons of crushed soapstone—essentially recycled waste—to store 100 megawatt-hours of heat, delivering 1 megawatt of thermal power to the local district heating network.

The sand battery works by converting surplus renewable electricity into heat, which is stored in the rock at temperatures up to 600°C.

The system can supply nearly a week’s worth of heating during Finland’s harsh winters and up to a month in summer, with heat losses limited to just 10–15%.

The technology has allowed Pornainen to eliminate oil from its heating supply and cut wood chip use by 60%, reducing annual carbon emissions by nearly 70%—about 160 tons of CO₂.

Unlike costly lithium-ion batteries, the sand battery is built from cheap, abundant materials and is simple to construct.

The project, which took about a year and involved over 100 workers, stands 13 meters tall and 15 meters wide.

Finland’s sand battery is part of a broader surge in thermal battery innovation. Scotland-based Sunamp uses phase-change materials for hot water storage; Electrified Thermal Solutions has developed bricks that store heat up to 2,000°C for industrial use; and Fourth Power is working on graphite blocks that can hold electricity as heat at 2,400°C.

These technologies offer scalable, low-carbon alternatives to fossil fuels for heating and industrial processes.

It sets a new benchmark for municipal and industrial energy storage as Europe accelerates its transition to renewables.

With energy prices in Finland among the lowest in Europe, the economics of sand batteries look increasingly appealing, promising scalable, low-carbon heating for cities worldwide.

Edited by Annette George