A Finnish municipality has installed the world’s largest sand battery, offering a sustainable solution to short-duration energy storage and significantly reducing carbon emissions in district heating.
A small municipality in southern Finland has taken an innovative step towards sustainable energy solutions by installing the world’s largest “sand battery,” designed by the company Polar Night Energy. This innovative thermal energy storage system is housed within a vast steel container roughly 30 by 12 meters in size, effectively forming a giant sandpit that harnesses excess renewable energy to provide heating for the town.
The sand battery operates by heating sand to temperatures as high as 600 degrees Celsius (1,112 degrees Fahrenheit) through closed-loop heat transfer pipes. The heat is then retained within the sand, insulated by layers of steel and an insulating barrier, allowing the stored thermal energy to be preserved for potentially months. When needed, cool air is blown through the pipes to capture this heat, which can then be converted into hot water, steam, or warm air to supply the local district heating network.
Renewable energy sources such as solar and wind face the challenge of intermittent power generation, as their availability fluctuates seasonally and daily. This makes effective energy storage critical in balancing supply and demand. According to Matteo Chiesa, a professor of mechanical and nuclear engineering at Khalifa University of Science and Technology, the sand battery represents a robust solution to one of the largest obstacles in scaling renewable energy: storage.
The system installed in Pornainen boasts a heating power capacity of 10 megawatts, meaning it can deliver 10 million joules of energy per second. This powerful output temperature range between 60 and 400 degrees Celsius (140 to 752 degrees Fahrenheit) makes it sufficiently flexible for various heating needs. Practical experience in Finland shows promising results, suggesting potential for replication in other locations with similar energy storage requirements.
Sand’s use as a heat-retaining medium is rooted in ancient practices like brick ovens, prized for sand’s high heat tolerance and excellent capacity to retain warmth. The widespread availability of sand globally adds to the appeal of this method. However, as a thermal energy storage system, the sand battery does not generate electricity directly but stores heat energy produced from surplus renewable power. It’s then used during periods when energy supply dips below demand.
While the technology shows promise, challenges remain, especially around the cost and scalability of the design for residential or smaller-scale use. Chiesa notes that current configurations, which incorporate metal materials for durability and heat transfer, drive up expenses that might be prohibitive for household adoption. Ideally, enhancements in sand porosity could allow more efficient air distribution without the need for costly materials, broadening potential applications.
Currently, the sand battery serves as a short-duration storage system primarily to manage fluctuations in wind power, rather than seasonal energy storage. Still, its capability to conserve heat over extended periods offers a powerful solution for future seasonal storage needs, such as storing summer solar energy to meet winter heating demands—arguably the most pressing seasonal energy challenge.
The sand battery in Pornainen is integrated with the local district heating network managed by Loviisan Lämpö, a Finnish energy firm. This facility acts as the primary heat production plant for the municipality, marking a significant advancement in non-combustion heat production and significantly reducing carbon emissions. According to Polar Night Energy, the system cuts carbon emissions from Pornainen’s heating network by about 70%, offering a clear environmental benefit in line with Finland’s and broader European goals to achieve net-zero emissions by 2050.
The official inauguration of the sand battery was attended by Finland’s Minister of the Environment and Climate, Sari Multala, highlighting its importance to the nation’s climate strategy. Polar Night Energy continues its work advancing sand battery technology, having already developed the world’s first commercial sand battery in Western Finland, proving the scalability and applicability of this technology within district heating frameworks.
As the world urgently seeks sustainable and reliable energy storage solutions to complement variable renewable generation, Polar Night Energy’s sand battery represents a compelling innovation. Its capacity to store large amounts of thermal energy with minimal environmental impact could become integral to transitioning away from fossil fuels for heating, especially in colder climates where heating demand is substantial.
