How the world's largest sand-battery in Finland is helping the energy transition

In southern Finland, near the town of Pornainen, a groundbreaking thermal energy storage system has been operating since 2025. Known as the world's largest sand battery, this innovative solution helps address one of the key challenges of the energy transition, storing surplus renewable electricity as heat. The facility, which serves a community of around 5,000 residents, stores excess power generated by wind and solar installations during periods of low demand and high supply, converting it into usable heat for winter heating needs. The system operates by using cheap electricity, typically produced when wind turbines and solar panels generate more than can be consumed immediately. During these times, electrical energy is used to heat air, which then flows through a bed of finely crushed sandstone. This process raises the temperature of the material to between 500 and 600 degrees Celsius. The stored heat is retained due to effective insulation and can be released later when needed, such as during cold winter days. Unlike traditional batteries that store electricity directly, this system stores thermal energy instead. It enables a temporal decoupling of electricity generation and consumption, allowing for efficient utilization of renewable resources. This principle mirrors how some households charge electric vehicles during off-peak hours. The implementation of this technology marks a significant shift in the local district heating network of Pornainen. Previously, much of the district heating was supplied by oil and wood chips. Now, the sand battery covers a large portion of the area’s heating needs without combustion. According to data from the company managing the project, greenhouse gas emissions from the district heating network have dropped by nearly 70 percent. The usage of wood chips has also decreased by approximately 60 percent, although a biomass power plant remains available as a backup for peak loads, though it is used far less frequently. Tommi Eronen, a representative of Polar Night Energy, the firm behind the development of the system, emphasizes the importance of such thermal storage solutions for the future. As the energy landscape continues to evolve, he suggests that these types of systems will play a crucial role in ensuring reliable and sustainable energy supply. The facility is operated by Loviisan Lämpö, a district heating provider. The project reflects broader efforts in Finland to reduce reliance on fossil fuels and enhance the efficiency of renewable energy integration. Given Finland’s proximity to Russia and potential disruptions in energy supplies, the reliability of locally sourced and stored energy becomes even more critical. As the world seeks to transition towards cleaner energy sources, innovations like the sand battery in Pornainen offer promising pathways. They demonstrate how simple materials and clever engineering can contribute significantly to achieving climate goals while maintaining energy security. The success of this initiative could serve as a model for other regions aiming to advance their energy transitions with practical and scalable solutions.