Finland’s Giant Sand Battery Supplies Heat to Pornainen

A 13-meter-tall, 15-meter-wide facility in the southern Finnish town of Pornainen uses 2,000 metric tons of crushed soapstone to store thermal energy. Developed by Polar Night Energy and commissioned by the district-heating company Loviisan Lämpö, the sand battery can deliver about 100 megawatt-hours of heat—enough for the town’s 5,000 residents for nearly a month in summer and roughly a week in winter. The system was launched last year as part of a local effort to replace oil- and wood-chip-based heating with a combustion-free alternative.

CNBC

When wind or solar generation is abundant and electricity prices are low, the grid supplies power to heat the sand to very high temperatures. The heavily insulated silo retains that heat for days or weeks. Heat exchangers then convert the stored thermal energy into steam that warms water for the district-heating network.

CNBC

Polar Night Energy estimates that the sand battery has cut greenhouse-gas emissions from the local heating network by almost 70 % and reduced wood-chip consumption by about 60 %. An existing wood-chip plant remains as a backup for peak demand. The project is roughly ten times larger than a 2022 pilot in Finland, suggesting that sand-based electro-thermal storage could be replicated in other regions that rely on fossil-fuel heating.

CNBC

Tommi Eronen, CEO of Polar Night Energy, says the technology addresses the “intermittency” challenge of renewable power by providing large-scale storage without rare-earth materials. Jan Rosenow, professor of energy and climate policy at the University of Oxford, notes that sand batteries avoid the limited storage duration of lithium-ion batteries, offering “days and maybe even weeks” of capacity. Mikko Paajanen, CEO of Loviisan Lämpö, emphasizes that the system separates electricity procurement from heat production, enabling the town to exploit low-price electricity for heating needs.

CNBC

• “We're changing from a world where big power plants were doing the energy production to where solar and wind are producing the energy, then we need a massive amount of storage,” — Tommi Eronen, CEO of Polar Night Energy

CNBC

• “You don't need rare earths, critical raw materials and the beauty is you can also charge up the battery when the electricity is cheap and discharge whenever you need the heat,” — Jan Rosenow, professor of energy and climate policy at the U

CNBC

• “The main thing is that we can separate the electricity procurement from the district heating production because now we are able to deliver this heating during the wintertime for one week, with one charge of the battery, and during the summertime, it even lasts as long as one month,” — Mikko Paajanen, CEO of Loviisan Lämpö

CNBC