Finland’s Radical Renewable Energy Solution

In the quiet town of Pornainen, southern Finland, a groundbreaking innovation is tackling one of the most persistent challenges in the renewable energy revolution: intermittency. The world’s largest commercial sand battery, a towering structure of insulated metal and sand, is demonstrating a novel approach to storing clean energy and ensuring a reliable heat supply.

Standing an imposing 13 meters tall and 15 meters wide, this facility houses 2,000 metric tons of crushed soapstone, a readily available and non-toxic material. This mass of stone acts as a thermal energy reservoir, capable of storing up to 100 megawatt-hours of heat. The implications for the town’s 5,000 residents are significant: the sand battery can meet nearly a month’s worth of heating demand during the summer and approximately one week’s worth during the colder winter months.

Commissioned by Loviisan Lämpö, a local district heating company, and developed by Polar Night Energy, the sand battery became operational last year. It represents a strategic shift towards flexible heat production technology, aiming to drastically reduce the carbon emissions traditionally associated with the town’s district heating network. Polar Night Energy estimates that this single project has already cut greenhouse gas emissions from the network by nearly 70% and reduced the reliance on wood chips by about 60%. While an existing wood-chip power plant remains as a backup and for peak load management, the sand battery is now the primary source of clean heat.

“We are transitioning from a paradigm of large power plants dominating energy production to one where solar and wind are at the forefront,” explained Tommi Eronen, CEO of Polar Night Energy, in a recent interview. “This shift necessitates a massive expansion of energy storage solutions. We envision sand battery technology playing a substantial role in this future, crucially, without the need for rare earth materials often found in conventional chemical batteries like lithium-ion.”

The Pornainen project is a significant advancement, roughly ten times the scale of an earlier sand battery pilot in Finland launched in 2022. This scalability underscores the potential for sand batteries to become a significant factor in decarbonization efforts, both locally and on a global scale. While battery storage is widely recognized as a linchpin in the global energy transition, sand batteries specifically show promise for regional heat storage. However, scaling this technology inevitably presents hurdles, including the efficiency of converting stored heat back into electricity and its energy density compared to more established battery types.

“We’re changing from a world where big power plants were doing the energy production to where solar and wind are producing the energy, then we need a massive amount of storage,” Eronen added. “Hopefully, a big portion of those storages could be sand battery-type of storages where we don’t need rare earth materials, like in many chemical batteries, such as lithium-ion batteries.”

At its core, the sand battery functions much like an oversized, highly insulated thermos. The process begins by capturing electricity from the grid during periods of abundant wind or solar generation. This electricity is then used to heat the sand within the silo to extremely high temperatures. The robust insulation of the silo ensures that this heat is retained for extended periods – days or even weeks. When heat is needed, it is discharged through heat exchangers, which warm water for the danich district heating network.

“There are three key steps, and the magic lies in the sand’s ability to create a delay between the time electricity is used and when the heat is utilized,” stated Annette Höglund-Dönnes, Chief Commercial Officer at Polar Night Energy. “This delay is the fundamental business advantage. It allows us to heat the sand when electricity prices are low and then leverage that stored heat when producing steam from the grid would be prohibitively expensive, such as during peak demand hours.”

Höglund-Dönnes drew a parallel to charging a mobile phone overnight, highlighting the cost-saving aspect of utilizing cheaper, off-peak electricity. The company has reportedly received inquiries from potential partners on every continent, particularly from regions heavily reliant on fossil fuels like coal and oil. This interest reflects the growing global urgency to find sustainable alternatives to combat climate change, a crisis repeatedly underscored by scientific consensus, with fossil fuel combustion identified as its primary driver.

Höglund-Dönnes drew a parallel to charging a mobile phone overnight, highlighting the cost-saving aspect of utilizing cheaper, off-peak electricity. The company has reportedly received inquiries from potential partners on every continent, particularly from regions heavily reliant on fossil fuels like coal and oil. This interest reflects the growing global urgency to find sustainable alternatives to combat climate change, a crisis repeatedly underscored by scientific consensus, with fossil fuel combustion identified as its primary driver.

The efficacy of electro-thermal storage technologies like sand batteries is gaining recognition among experts. Jan Rosenow, a professor of energy and climate policy at the University of Oxford, believes such solutions are poised for widespread adoption. “The beauty of these systems is their reliance on abundant, non-critical materials, and the ability to charge when electricity is cheap and discharge precisely when heat is needed,” Rosenow explained. “Furthermore, they offer long-duration storage capabilities, potentially lasting days or even weeks, a significant advantage over the shorter durations typical of lithium-ion batteries.”

Critics of renewable energy often highlight the inherent intermittency of sources like solar and wind power – they generate electricity only when the sun shines or the wind blows. Energy storage systems, including battery technologies, are crucial for smoothing out these fluctuations, absorbing surplus renewable generation and releasing it during periods of lower output. Mikko Paajanen, CEO of Loviisan Lämpö, emphasized how the sand battery directly addresses this challenge.

“The most significant benefit is the decoupling of electricity procurement from district heating production,” Paajanen stated. “We can now reliably deliver heating throughout the winter for a full week on a single battery charge, and in the summer, this duration extends to a month. This allows us to capitalize on favorable low spot prices for electricity.”

Loviisan Lämpö aims to source between 55% and 60% of the municipality’s district heating from the sand battery in the coming months, a substantial increase from approximately 30% in the previous year. Finland’s Climate Minister, Sari Multala, lauded the Pornainen project as an “inspiring and innovative” example of how to overcome energy storage challenges.

“During my visit to the facility at its inauguration, I understood that they are actively exploring solutions for potential future electricity generation as well,” Minister Multala commented. “This would indeed be groundbreaking and offer immense value to many.”