Industrial-scale sand battery to green Finnish district heating

Finnish energy storage developer Polar Night Energy has built an industrial-scale sand battery in the municipality of Pornainen for the Loviisan Lämpö’s district heating network.

The new sand battery, claimed to be the world’s largest, delivers 1MW of thermal power and offers a storage capacity of 100MWh.

The project is expected to reduce annual CO₂-equivalent emissions from the local heating network by around 160 tonnes, cutting emissions in Pornainen’s district heating by nearly 70%.

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

“Our goal is to be climate neutral by 2035, and the Sand Battery is a major step toward that,” Paajanen added.

The launch of the sand battery will allow the complete phase out of oil currently used in the Pornainen’s heating network, and the consumption of wood chips will decrease by approximately 60%. The existing biomass boiler will continue to serve as a backup and will support the battery during peak demand periods.

The sand battery is a high-temperature thermal energy storage system that stores electricity as heat in sand or similar solid materials. It can be used to produce heat for both district heating networks and a wide range of industrial processes.

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The battery stands about 13 meters tall and 15 meters wide, and it uses approximately 2,000 tonnes of crushed soapstone as its thermal storage medium – a by-product from the production of Tulikivi’s heat-retaining fireplaces.

In summer, the battery can cover almost a month’s heat demand in Pornainen, and in winter, close to a week.

Liisa Naskali, chief operating officer of Polar Night Energy, commented: “Combustion is not a sustainable option for the climate or the environment. 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.”

According to Polar Night Energy, a key part of the battery’s profitability lies in optimising its operation according to electricity prices and Finland’s grid operator Fingrid’s reserve markets. In doing so, it helps to support power grid stability, allowing electricity usage to be optimised over several days or even weeks.

The optimisation of the battery is handled by Elisa, a Finnish telecommunications and digital software services company.

Jukka-Pekka Salmenkaita, vice president of AI and Special Projects at Elisa Industriq, said: “Our AI-driven solution automatically identifies the most economically viable moments to charge or discharge the Sand Battery. This brings Loviisan Lämpö significant savings and revenue, making the Sand Battery a truly profitable investment.”

Polar Night Energy acted as the main contractor for the project and construction took about a year to complete.

Loviisan Lämpö is owned by CapMan Infra, a fund managed by the private equity firm CapMan.

Sauli Antila, investment director at CapMan Infra, commented: “From an investor’s perspective, this technology holds tremendous potential: it can participate in electricity reserve markets, reduce dependency on single energy sources in heat production, and serves as a great example of sector integration between electricity and heat.”

Polar Night Energy is currently in active discussions with both Finnish and international partners about new sand battery projects. Earlier this spring, the company announced a pilot in Valkeakoski to explore the conversion of stored thermal energy back into electricity.

Originally published on Power Engineering International.