World’s largest sand battery commissioned in Finland

The world’s first industrial-scale sand battery has been commissioned in Pornainen, Finland. It will use surplus renewable energy to generate heat, which will then be supplied to the local district heating network.

The sand battery, which delivers one megawatt of thermal energy and has a storage capacity of 100 megawatt-hours, was installed for the district heating system in the municipality of Pornainen, operated by Loviisan Lämpö.

A sand battery is a high-temperature thermal energy storage system, first developed by the start-up Polar Night Energy.

Finding ways to store energy from variable renewable sources is one of the biggest challenges of the energy transition. In the case of the battery developed by Polar Night Energy, the storage medium is sand or alternative sand-like materials.

The battery uses renewable electricity to power a heater, which then blows hot air into the sand. The sand is heated to between 500 and 600 degrees Celsius and retains that heat. The stored energy can be used for district heating, but also for industrial processes.

A prototype of the battery was installed in 2022 at the Valkeakoski power plant in the town of Kankaanpää, Finland. The new battery in Pornainen is ten times larger than the prototype and represents the first industrial-scale implementation of this technology.

It is 13 meters high and 15 meters wide, filled with 2,000 tons of crushed soapstone, a by-product from the production of fireplaces by Finnish company Tulikivi. During winter, the battery can cover heating needs for about a week.

Emissions in the district heating sector will be reduced by 70% thanks to the battery

“The Sand Battery means a lot to Loviisan Lämpö. It allows us to drastically reduce our emissions and improve the reliability of heat production,” says Mikko Paajanen, CEO of Loviisan Lämpö.

The company aims to become climate-neutral by 2035, and the battery will help it cut emissions by 160 tons of CO₂ equivalent – a reduction of nearly 70% in the district heating sector.

Thanks to the battery, the company will stop using oil for district heating completely, while the consumption of wood chips will be reduced by about 60%. A biomass boiler will be used as a backup during periods of peak demand, the company said.

“This project is a powerful example that effective solutions for mitigating climate change do exist. Loviisan Lämpö is a great example of a company bold enough to invest in new technologies,” says Liisa Naskali, Chief Operating Officer of Polar Night Energy.

Sand battery stabilizes the power grid and contributes to the circular economy

Advancing the circular economy and energy transition requires cross-sectoral cooperation, which the sand battery clearly demonstrates. It is not just a heat storage system – it’s a tool for grid balancing, emissions reduction, smart energy management, and better resource use.

A key factor in the sand battery’s cost-effectiveness lies in optimizing its operation according to electricity prices set by Finnish grid operator Fingrid. In this way, the battery also contributes to the stability of the power grid, which is essential for the further development of wind and solar power.

Thanks to its large storage capacity, the system enables optimization of electricity use over several days, or even weeks.

The thermal storage material in sand batteries can include by-products from industrial or mining processes, avoiding the exploitation of natural resources.

Polar Night Energy is currently in talks with partners in Finland and abroad about new projects. Earlier this year, it announced a pilot project in Valkeakoski to explore the possibility of converting stored heat back into electricity.