“In a bold move that could reshape the energy landscape,” Denmark has unveiled a 1 GWh molten salt battery capable of powering 100,000 homes for 10 hours. Developed by Hyme Energy in collaboration with Sulzer, this is one of the world’s first large-scale, long-duration thermal storage systems that’s not just theoretical—it’s fully operational and commercially viable.
This project marks a significant advance in storing renewable energy in a way that’s reliable, affordable, and safe. By using common industrial byproducts and heat-based technology, the system addresses the challenge of intermittent wind and solar power, supports decarbonization of heavy industry, and builds a more resilient, flexible grid for the future.
What is a molten salt battery?
“At its core, a molten salt battery is a type of thermal energy storage system.”
Unlike lithium-ion batteries that store energy through electrochemical processes, molten salt batteries use heat. Specifically, they rely on molten hydroxide salts heated to around 600°C (1,112°F), stored in a dual-tank system—one for hot liquid and one for cooler return liquid. When excess renewable energy is available, it’s used to heat the salt. Later, the stored heat generates steam, which can either power a turbine to produce electricity or be delivered directly into industrial processes requiring high temperatures.
Denmark’s MOSS demonstrator: Specs and performance
Launched in April 2024 in Esbjerg, Denmark’s MOSS demonstrator plant holds 1 GWh of thermal energy—enough to supply 100,000 homes with power for 10 hours. It achieves up to 90% efficiency when used in cogeneration setups, where both heat and electricity are needed, and delivers 40% efficiency when used solely to generate electricity, which is still a strong result for a thermal system. Impressively, the system can store heat for up to two weeks, making it ideal for seasonal grid balancing and backup. Unlike a pilot or trial, this facility is live, operational, and ready for replication.
Turning industrial waste into clean energy
One of the project’s most innovative aspects is its use of molten hydroxide salt—a byproduct of chlorine production in Denmark. Instead of treating it as hazardous waste, Hyme Energy found a way to turn it into a stable, clean, and abundant heat storage medium. This material boasts a high heat capacity, allowing more energy to be stored per unit of volume. It’s also non-toxic, non-flammable, and cost-effective. Its ability to function at extreme temperatures makes it well-suited for both industrial and grid-scale energy needs.
Two-tank design: The key to heat retention
“One of the biggest challenges with thermal batteries is heat loss over time.”
To address this, Denmark’s molten salt battery uses a two-tank system. The hot tank stores energy-rich salt, while the cold tank holds it after the heat is extracted. With advanced insulation and thermal management, the system loses very little heat—even over days or weeks. This architecture enables reliable, long-duration storage with minimal efficiency drop-off, which is critical for managing renewable energy’s variable output.
Scaling to industry: The Holstebro expansion
Riding on the success of the Esbjerg facility, Hyme Energy is now building a 200 MWh molten salt plant in Holstebro. Its goal is to directly supply heat to Arla Foods, one of Europe’s largest dairy producers. This move will reduce Arla’s gas consumption by 50%, significantly cut carbon emissions, and save the company over €3 million (about $3.1 million USD) in annual energy costs. It’s a powerful example of how molten salt batteries can help large industries decarbonize, aligning with broader EU climate targets.
Sulzer’s role: Making molten salt flow at scale
Sulzer, a global engineering company, plays a vital role in making molten salt energy systems viable at scale. They provide highly efficient pumps that can handle extreme heat and corrosive conditions, thermal circulation systems that minimize energy loss, and technology that ensures these batteries can be scaled up for global energy grids. Their expertise helps transition this system from a single project into a repeatable solution for worldwide deployment.
Why it beats lithium-ion for grid storage
While lithium-ion batteries dominate in phones, laptops, and electric vehicles, they struggle with grid-scale storage needs—especially for long durations. Molten salt batteries offer a compelling alternative: they are cheaper to scale, can store energy for up to two weeks, and don’t rely on rare or toxic materials. This makes them particularly attractive to countries investing heavily in wind, solar, or nuclear energy, which all need stable, flexible storage solutions to support their grids.
Industrial decarbonization: A hidden climate solution
“Most people associate energy storage with electricity. But industry runs on heat.”
Major industrial sectors—like cement, steel, food, and chemicals—consume huge amounts of heat, typically generated with fossil fuels. These processes require temperatures between 150°C and 800°C. Molten salt batteries are ideally suited for this task, providing clean, consistent heat and marking one of the first real steps toward eliminating fossil fuels from industrial heating. This overlooked piece of the climate puzzle is essential for meeting global net-zero goals.
Can other countries adopt this tech?
Yes, and they should. Molten salt batteries use readily available materials and fit into existing industrial infrastructure. Their modular design means they can scale from small applications to massive multi-GWh setups. They also work seamlessly alongside solar, wind, and even nuclear power sources. Countries with industrial salt waste or a growing renewable energy sector—like the United States, Germany, China, and India—are in an excellent position to adopt this model.
What’s next?
While molten salt storage is promising, it’s not without its challenges. Upfront installation costs remain high, and there’s still limited public awareness and policy support. More long-term performance data is needed to build investor confidence, and skilled operators must be trained to manage these systems. Nonetheless, Denmark’s early success has sparked global interest, with new projects expected soon in Germany, the U.S., and Japan.
In summary
The 1 GWh molten salt battery in Esbjerg is more than just an engineering breakthrough—it’s a practical, scalable solution to some of the world’s most pressing energy challenges. It is affordable, safe, efficient, and low-carbon. Most importantly, it proves that we can turn industrial waste into clean, grid-scale energy.
“If the rest of the world takes note, molten salt might just be the missing link in the global clean energy puzzle.”
IBM has unveiled the World’s Smallest Computer, smaller than a grain of salt
Cutting-Edge SimulationSupercomputer Aurora to Revolutionize Nuclear Reactor
AI develops a battery design that reduces lithium usage by 70 percent
