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The sand battery developed by Polar Night Energy for Loviisan Lämpö completed its first year of operation in Pornainen, Finland, achieving a 70% reduction in greenhouse gas emissions from the local district heating network.
Furthermore, the installation met the performance objectives and design specifications anticipated since its commissioning in June 2025. The system operates as the primary source of thermal production for the municipal network.
How Polar Night Energy’s Sand Battery Works
The sand battery stores renewable energy as heat using sand or similar materials. In this case, the plant uses 2,000 tons of crushed steatite as a thermal storage medium, within a structure 13 meters high and 15 meters wide.
Likewise, the system allows energy to be stored for days or weeks, a significant advantage for utilizing renewable electricity when market prices are low. According to project data, the battery has been charged with electricity 70% to 80% cheaper than the average spot price, with some months seeing a difference exceeding 90%.
The company informed Inspenet that, during its first year, the plant registered no interruptions in district heating supply. For Pornainen, a municipality of about 5,000 inhabitants, this means greater energy security, more stable prices, and reduced dependence on fossil fuels.
Similarly, the system achieved an efficiency exceeding 85%, maintaining 100% supply reliability in the district heating network. In terms of energy impact, it allowed for a 60% reduction in biomass consumption and completely eliminated the use of oil.
It also allows for the expansion of the district heating network. New municipal buildings, such as a sports hall and a renovated school, can be connected to the system thanks to the increased thermal capacity.
International Recognition
The Pornainen project has received global attention and various accolades within the energy and technology sectors.
These include its inclusion in TIME’s list of the best inventions of 2025 in the green energy category and its selection by Popular Science as one of the year’s top 50 engineering innovations.
Additionally, the initiative was awarded by Mission Innovation within the net-zero industries program, with special recognition for industrial electrification. In Finland, it also won the Breakthrough award at the 2026 Technology Awards granted by academic engineering organizations.
International bodies such as the World Economic Forum have highlighted the project as a model for the global energy transition, while Forbes analyses emphasize its capacity to store thermal energy on a large scale and significantly reduce carbon emissions.
Although the Pornainen case focuses on district heating, Polar Night Energy and its partners see potential for applying this technology in industrial processes that require high temperatures. Many operations still rely on natural gas or oil to generate steam or process heat.
Source and photo: Polar Night Energy
