Finland Activates World's Largest Commercial Sand Battery for District Heating
The 100 MWh soapstone storage system in Pornainen cuts heating emissions by 70% and demonstrates scalable long-duration thermal storage.
Pornainen, Finland, has activated the world's largest commercial sand battery, storing renewable electricity as heat in crushed soapstone and marking a breakthrough in long-duration energy storage.
Developed by Polar Night Energy and commissioned by utility Loviisan Lämpö, the facility decarbonizes district heating without lithium-ion batteries or rare earth materials.
Scale and Specifications
The battery stands 13 meters tall and 15 meters wide, holding 2,000 metric tons of crushed soapstone—a byproduct from Tulikivi fireplace manufacturing. The system delivers 1 MW of thermal power with 100 MWh of storage capacity, covering roughly one month of summer heating demand or one week in winter.
Emissions Impact
The project cuts greenhouse gas emissions from Pornainen's heating network by nearly 70% while reducing wood chip consumption by approximately 60%.
"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," said Tommi Eronen, CEO of Polar Night Energy.
The technology converts excess wind and solar electricity into heat, stored in soapstone and discharged as hot water for the district heating network. This enables municipalities to purchase electricity during low-price, high-renewable periods and use it when heating demand peaks.
"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," said Mikko Paajanen, CEO of Loviisan Lämpö.
Broader Implications
Sand batteries offer a low-cost alternative to chemical batteries for thermal storage. Unlike lithium-ion systems, they use abundant materials and avoid rare earth supply chain constraints. The Pornainen installation demonstrates commercial viability at municipal scale, offering a replicable model for communities decarbonizing heating infrastructure.
By decoupling electricity procurement from heat production, the system lets towns buy power when renewable generation is highest and prices are lowest, then discharge stored heat when demand peaks. This flexibility addresses the intermittency challenge hindering wind and solar adoption while stabilizing local grids.
Finland's sand battery success could accelerate adoption of similar thermal storage solutions across Northern Europe, where district heating networks serve millions and decarbonization targets grow increasingly urgent.