Europe’s storage gap is becoming a market problem as well as an energy security concern. Solar and wind output can exceed demand at midday, pushing prices below zero, while evening shortfalls leave power systems reliant on imported fuel. The mismatch matters because electricity generated at one time isn’t automatically available when households and businesses need it later. Finland’s large-scale sand battery offers one way to store renewable energy as heat for longer periods, with fewer supply-chain ties to battery minerals. It’s a useful test of how storage can serve a specific local need.
Storage capacity trails renewable growth
The European Union has expanded solar and wind generation, but storage hasn’t kept pace. Renewables now supply 44 percent of EU electricity, while the bloc imports around 55 percent of its total energy, including oil and gas, according to Euronews. Those figures describe different parts of the energy system: renewable electricity is growing, while imported fuels still supply a large share of total energy. Without enough storage and flexibility, imported gas remains a key source of power when renewable output falls. That leaves a gap between producing more clean electricity and reliably using it when it’s needed.
That imbalance also affects electricity prices. When renewable generation exceeds demand and the grid can’t absorb the surplus, negative prices can result. Such prices signal that electricity is available at a time when the system has limited ability to use, move, or store it; they don’t by themselves show that power will be available later. PV magazine has warned that weather, strong solar output and limited flexibility could widen the gap between midday production and evening demand in Europe’s third quarter of 2026. The underlying issue is timing.
The European Commission has set a target of 200 gigawatts of storage capacity by 2030, up from 55 GW currently. The comparison underscores the scale of the buildout: the United States has 137 GW of grid-scale storage, while China’s installed capacity is nearly 213.3 GW. Those figures show how much expansion Europe is contemplating, but capacity totals alone don’t reveal how long systems can store energy or what form that energy takes. A short-duration battery and a thermal store may both add capacity, yet serve different needs. The target will depend on deploying a mix of systems that can address the timing and location of surplus generation.
Sand stores heat rather than electricity
Lithium-ion batteries are expected to supply much of Europe’s new storage, but their typical storage duration of up to about four hours limits their role in balancing renewable output across longer periods. Their supply chains are also heavily concentrated in China, leaving Europe exposed to the kind of dependence it’s seeking to reduce in energy markets. Sand-based storage addresses a different part of that problem: it turns electricity into heat, which can be held and used later where a heating network can take it. That distinction matters. Stored heat isn’t a direct substitute for electricity when the demand is for electrical power.
In Pornainen, Finland, district heating company Loviisan Lämpö commissioned what the source describes as the world’s largest sand battery, built by Polar Night Energy. The town has about 5,000 residents. The system stores energy as heat, and its capacity can cover nearly a month of the town’s heating demand in summer or as much as a week in winter. Those seasonal comparisons help explain the installation’s intended role: shifting energy into periods when heating demand can be served from stored heat. They don’t establish how the system would perform in other towns, where network design, local energy supply and demand may differ.
Polar Night Energy CEO Tommi Eronen has framed the project as a response to a power system increasingly supplied by variable renewables. “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 told CNBC. Eronen added that sand-based systems could avoid rare earth materials used in some chemical batteries, including lithium-ion. The case for the technology therefore rests on both its heat-storage function and its material profile. (And this is the part most people overlook: avoiding one set of supply-chain dependencies doesn’t make a system independent of all industrial inputs.)
A complement to battery storage
The Finnish installation is less energy-efficient than lithium-ion batteries, according to the source, and it serves a different purpose: supplying heat through a district heating network. Efficiency is only one part of whether a storage system fits a particular job. A system that stores heat may still be useful where that heat can meet local demand, even if it isn’t the best option for returning electricity to the grid. Polar Night Energy officials say the project has reduced greenhouse gas emissions from the town’s previous heating network by almost 70 percent. That’s a reported result for this installation, not evidence that the same reduction will follow everywhere.
That result makes the project relevant to places where heating demand can be met with stored thermal energy. If you’re working in this space, the practical question is whether a local heating network can use the stored heat at the times it’s available. The project doesn’t establish that sand batteries can replace grid-scale electrical batteries or solve Europe’s broader storage shortfall. Their potential lies in adding another storage option, particularly where renewable electricity can be converted into heat and used later. A narrower role, but a meaningful one.
What the project could mean for Europe
Europe’s challenge is to expand storage quickly enough to absorb surplus generation, reduce reliance on imported fuels and manage demand when renewable output dips. Finland’s project shows how a relatively simple material can serve part of that task. This is more significant than it looks: storage discussions often focus on electricity capacity, while this installation shows how local heat demand can also be part of the response. And yet, the project’s reported emissions reduction and seasonal capacity figures don’t settle the question of cost or suitability elsewhere; the source provides no basis for drawing those conclusions.
Its broader value will depend on whether similar systems can work economically across other district heating networks and local energy systems. That will require matching storage to the demand it’s meant to serve, rather than treating every added unit of capacity as interchangeable. The sand battery offers a route for storing renewable energy as heat. Whether that route can scale beyond a single town remains to be seen.