This successful implementation of renewable energy storage solutions could save over 100 million tons of CO2 equivalent emissions by 2030 as the technology scales globally with planned international deployments.
Finland has successfully deployed the world’s largest sand battery as part of innovative renewable energy storage solutions that cut carbon emissions by nearly 70 percent. The massive 15-meter-wide system in Pornainen can store enough thermal energy to meet the town’s heating needs for an entire month during summer.
The 100 megawatt-hour thermal energy storage system captures excess electricity from solar panels and wind turbines when production exceeds demand. This industrial-scale solution from Finnish company Polar Night Energy now serves as the primary heat source for the town’s district heating network, warming homes, offices, schools, and public buildings.
The technology addresses a fundamental challenge facing renewable energy storage solutions worldwide: how to capture variable renewable electricity and release it when needed. Sand-based systems cost approximately $25 per kilowatt-hour of storage — about a quarter the price of lithium-ion batteries, making them economically attractive for communities seeking sustainable heating alternatives.
The sand battery works through resistive heating, converting excess renewable electricity into thermal energy. When solar panels produce more power than needed or wind turbines generate surplus electricity, that energy heats sand stored in a tall tower. The sand reaches temperatures around 500 degrees Celsius and can hold that heat for days or even months.
The CEO of Loviisan Lämpö, which operates the heating network, describes the sand battery as a major step toward the company’s goal of becoming climate neutral by 2035. The system will reduce wood chip consumption by approximately 60 percent while maintaining the existing biomass boiler as backup power.
This installation represents a significant scaling up from Polar Night Energy’s first commercial sand battery, which launched in May 2022 in Kankaanpää. That smaller prototype proved these renewable energy storage solutions worked effectively when Russia cut off gas supplies to Finland after the country joined NATO.
The concept emerged in 2018 when Finnish engineers Tommi Eronen and Markku Ylönen recognized the need for affordable energy storage in northern climates. They discovered that ordinary sand grains could store massive amounts of energy at relatively low cost compared to lithium batteries.
The Pornainen sand battery stands 13 meters high and 15 meters wide, making it roughly 10 times larger than the Kankaanpää installation. The system uses computer algorithms to track how heat moves through the storage medium and determine exactly how much energy remains available for discharge.
When the town needs heat, the battery releases hot air that warms water circulating through the district heating network. This heated water flows through underground pipes to warm buildings throughout Pornainen, including the comprehensive school, town hall, library, and residential areas.
The town’s mayor reports that the project has proceeded smoothly and aligns with its commitment to sustainable energy solutions. Community members initially expressed curiosity about the technology, but have embraced the project as it progresses. The municipality has made carbon neutrality a key strategic target, and residents appreciate participating in innovative renewable energy storage solutions.
The system will eliminate approximately 160 tons of carbon dioxide equivalent emissions each year. During summer months, the battery can store nearly one month’s worth of heat demand, while winter storage capacity equals about one week of heating needs.
See also: Sand Battery: A Game-Changer in Energy Storage for Renewables
Environmental concerns about sand availability led the company to explore alternative materials for its renewable energy storage solutions. For the Pornainen project, Polar Night Energy chose crushed soapstone, a waste product from Tulikivi, a Finnish company that manufactures heat-retaining fireplaces.
This material choice demonstrates how sand batteries can work with various substances as long as they meet specific density and thermodynamic requirements. The flexibility allows the technology to use locally available materials and support circular economy principles by repurposing industrial waste.
Polar Night Energy secured funding to support expansion efforts and currently holds active discussions with Finnish and international partners interested in implementing similar systems. According to assessments, the technology may save over 100 million tons of CO2 equivalent emissions per year by 2030 as it scales globally.
The company announced plans for a pilot project in Valkeakoski to explore converting stored thermal energy back into electricity, potentially expanding applications beyond heating systems. This research project aims to create power-to-heat-to-power capabilities that could redefine energy storage.
The success in Pornainen builds on previous installations, including a pilot plant connected to Tampere city’s district heating network. Each project helps refine these renewable energy storage solutions and proves their viability for different community sizes across various geographic locations.
As renewable energy sources become more prevalent globally, storage solutions like sand batteries could play increasingly important roles in energy systems. The Finnish innovation offers communities a practical way to reduce fossil fuel dependence while utilizing locally available materials and supporting sustainability goals through proven renewable energy storage solutions.
