Finland has deployed the world’s largest commercial sand battery in the town of Pornainen, offering a radical solution to the critical intermittency problem of renewable energy. This innovative facility, developed by Polar Night Energy, stores 100 megawatt-hours of thermal energy using 2,000 metric tons of crushed soapstone, capable of heating the town for nearly a month in summer and a week in winter. The project significantly cuts carbon emissions and reduces reliance on fossil fuels, demonstrating a scalable, rare-earth-material-free alternative for massive energy storage.
In a groundbreaking move, a small town in southern Finland has deployed the world's largest commercial sand battery, aiming to conquer what many consider the most formidable challenge for renewable energy: its inherent intermittency.
This impressive facility, standing 13 meters tall and 15 meters wide, utilizes 2,000 metric tons of crushed soapstone to efficiently store clean energy as heat, providing a substantial 100 megawatt-hours of thermal energy.
Remarkably, this capacity is sufficient to meet nearly one month of heating demand for Pornainen's 5,000 residents during the summer, and approximately one week's demand in the colder winter months.
Commissioned by Finnish district heating company Loviisan Lämpö and engineered by Polar Night Energy, this colossal sand battery was inaugurated last year. Its primary goal is to integrate a flexible heat production technology, drastically cutting carbon emissions from the local district heating network. According to Polar Night Energy, the initiative has successfully reduced greenhouse gas emissions by nearly 70% and decreased the consumption of wood chips by approximately 60%. While an existing wood-chip power plant serves as a backup, Tommi Eronen, CEO of Polar Night Energy, highlighted that the sand battery now delivers combustion-free heating for the majority of the year, a significant shift from the town's prior reliance on burning oil and wood chips.
Eronen emphasized the paradigm shift in energy production: "We're transitioning from a world dominated by large power plants to one where solar and wind sources generate energy, necessitating a massive increase in storage capacity." He expressed optimism that "a significant portion of these storage solutions could be sand battery-type systems, which crucially do not require rare earth materials, unlike many chemical batteries such as lithium-ion counterparts."
The Pornainen undertaking represents a tenfold increase in scale compared to an earlier sand battery model launched in Finland in 2022. This expansion underscores the immense potential for sand batteries to contribute substantially to emission reductions, both within Finland and internationally.
While battery storage is universally recognized as crucial for the energy transition, sand batteries specifically demonstrate considerable promise for regional heat storage. However, scaling this technology is not without its challenges. Critics often point to concerns regarding their efficiency in converting stored heat back into electricity and their comparatively lower energy density when weighed against conventional battery technologies.
How Finland's Sand Battery Works
At its core, the sand battery technology functions much like a colossal thermos, engineered to store heat using a specialized material.
The process begins by drawing surplus electricity from the grid during periods of abundant wind or solar generation, which is then used to heat the sand to extremely high temperatures. Encased within a heavily insulated silo, this heat remains trapped for durations spanning days or even weeks. When needed, the stored heat is discharged through heat exchangers to warm water, which then circulates through the local district heating network.
"It's a three-step process, and the fundamental advantage lies in sand's ability to create a crucial delay between electricity consumption and heat utilization," explained Annette Höglund-Dönnes, Chief Commercial Officer of Polar Night Energy. She elaborated, "This delay offers a significant business advantage: you can heat the sand when electricity is inexpensive, then deploy that heat when generating it directly from the grid would be prohibitively costly, especially during peak daytime demand."
Höglund-Dönnes drew an analogy to charging a cell phone overnight, highlighting how off-peak electricity rates make the process economically viable.
When questioned about the potential for international replication, Höglund-Dönnes revealed that Polar Night Energy has received inquiries from teams across "every single continent," particularly from regions heavily reliant on fossil fuels like coal and oil. This global interest aligns with urgent warnings from climate scientists, who repeatedly stress that a drastic reduction in fossil fuel consumption is imperative to mitigate global heating, identifying the combustion of coal, oil, and gas as the primary catalyst of the climate crisis.
Addressing Renewable Energy's Intermittency Challenge
Jan Rosenow, a distinguished professor of energy and climate policy at the U.K.'s University of Oxford, concurred that electrothermal storage innovations, like sand batteries, are poised for widespread global adoption. "They eliminate the need for rare earths and critical raw materials," Rosenow stated to CNBC. "The elegance of this technology is its ability to charge when electricity prices are low and then discharge heat precisely when it's required. Crucially, it offers long-duration storage – not just a few hours like lithium-ion batteries, but potentially days, or even weeks."
A common critique leveled against renewable energy sources like solar and wind is their intermittent nature; they only generate power when environmental conditions are favorable. This is precisely where advanced energy storage systems, including sand batteries, become indispensable. They play a vital role in stabilizing the grid by absorbing surplus solar and wind generation during peak production and releasing it when output naturally declines.
Mikko Paajanen, CEO of Loviisan Lämpö, affirmed that the sand battery effectively addresses this critical hurdle in the energy transition. "The core advantage is the decoupling of electricity procurement from district heating production," Paajanen explained to CNBC. "We can now supply heating for a full week in winter, and up to a month in summer, on a single battery charge. This flexibility allows us to capitalize on low spot prices for electricity."
Paajanen further revealed Loviisan Lämpö's ambitious target: to generate between 55% and 60% of the municipality's district heating from the sand battery in the initial months of this year, a significant increase from approximately 30% in 2025.
Finland's Climate Minister, Sari Multala, hailed the Pornainen sand battery project as an "exceptionally inspiring" and pioneering solution to energy storage challenges. "During my visit to the plant's opening, I learned they are also exploring future applications for electricity generation, which would be truly groundbreaking and widely valued," Multala informed CNBC.
