In Finland, Polar Night Energy (a startup) and Loviisan Lämpö (a district heating company) plan to build an industrial-scale sand-based thermal energy storage system in the city of Pornainen.

The 1 MW sand battery will be able to store up to 100 MWh of thermal energy – a capacity equivalent to nearly a month's heating needs in summer and a week in winter in Pornainen.

Polar Night Energy says it is a large steel silo of sand (or a similar solid material) that is heated via a centrally buried heat exchanger. The sand battery acts as a high-capacity storage tank, storing large amounts of excess wind and solar energy. The energy stored in the sand is heat. The battery is about 13x15m in size. Development and construction is expected to take about 13 months.

Theoretically, this energy can be converted back into electricity, but the most efficient way is to use heat.

news sandbattery1.jpg
Sand battery station. Photo: EU

The sand battery will be integrated into Loviisan Lämpö's district heating network. The battery will be charged from the grid using charging algorithms developed by Polar Night Energy. The company says this will minimize the cost of electricity used for charging, while also meeting the demand from the district heating network.

The world's first commercial sand battery is located in a town called Kankaanpää, Western Finland. It is connected to the district heating network and heats buildings and family homes and the city swimming pool. The district heating network is operated by an energy company called Vatajankoski.

According to Polar Night Energy, the battery will also help reduce annual carbon dioxide emissions from Pornainen’s district heating network by nearly 70%. Liisa Naskali, CEO of Polar Night Energy, said the project was a significant step forward in scaling up sand battery technology.

Polar Night Energy says it will source a “soapstone” that conducts heat better than regular sand from Tulikivi, a Finnish company that specializes in heat-retaining heaters.

battery cat active.jpg
How sand batteries work. Photo: DM

In 2022, Polar Night Energy launched the world's first commercial sand-based high-temperature thermal storage system in the Finnish city of Kankaanpää, with a heating capacity of 100 kW and an energy capacity of 8 MWh.

In December 2023, the company announced a partnership with Nordic energy company Ilmatar to develop sand batteries capable of converting thermal energy into electricity.

Small island sets record for running entirely on renewable energy for 28 consecutive days El Hierro, a small island in Spain's Canary Islands, made history last summer when it ran entirely on renewable energy for 28 consecutive days.