World's largest sand battery to provide heat for Finnish town without using fossil fuels.

      A small town in Finland is set to eliminate fossil fuels from its heating network, thanks to a house-sized energy storage tank filled with sand. Finnish startup Polar Night Energy has recently activated this sand battery in Pornainen, a town located about an hour north of Helsinki. This system utilizes sand to store excess renewable energy in the form of heat, which will heat the homes and businesses of the 5,000 residents. It is projected to completely replace natural gas and oil in the local district heating network, reducing emissions by an estimated 70%.

      "This project serves as a strong demonstration that viable solutions for combating climate change are available," said Liisa Naskali, COO of Polar Night Energy. "Combustion is not a sustainable choice for the climate or the environment."

      The energy storage structure stands approximately 13 meters tall and 15 meters wide, containing 2,000 tonnes of crushed soapstone, a byproduct from the construction industry. This new battery is ten times larger than the startup's initial pilot plant in Pornainen, which was launched in 2022.

      When renewable energy sources are plentiful, such as on sunny or windy days, clean electricity is directed to the battery. Here, it powers a heater that circulates hot air through pipes into the large sand reservoir, heating it up to an impressive 600°C.

      Thanks to its insulated walls, this stored energy can last for weeks or even months. When required, the battery releases the hot air on demand, heating water in the district heating network. This heat can then be distributed to households, factories, and even swimming pools.

      “While we cannot single-handedly address the entire issue of climate change, we require a variety of solutions, and our sand battery is one of them,” Naskali stated in a video.

      With a power output of 100 MWh, Polar Night anticipates that the battery can heat the entire town of Pornainen for a week during winter, or an entire month in summer when energy demand is lower, all from just one charge. The town will also keep a biomass boiler that burns wood chips as a backup energy source during peak demand periods.

      It takes approximately four days to charge the sand battery from ambient temperature to 600°C. However, it is continuously replenished with excess renewable energy whenever available, so it seldom cools down to match the temperature of the surrounding air.

      Insulation panels covering the sand battery's exterior help retain heat for extended periods.

      Polar Night has indicated that it is currently in talks to install larger sand batteries both in Finland and internationally, with the goal of providing a cleaner alternative to fossil fuels for heating residential spaces.

      Heating represents around half of total energy consumption, according to the International Energy Agency (IEA). In Europe, most of this heat is derived from burning natural gas, oil, wood chips, or waste.

      For European towns, especially those with abundant renewable energy resources, sand batteries may present an accessible solution. If developed further, they could become a significant element of the energy storage portfolio, alongside other technologies like lithium-ion, gravity, hydropower, and CO2 domes.

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