Denmark Unveils 1 GWh Molten Salt Battery for Long-Duration Energy Storage

Denmark has unveiled a 1 GWh large-scale molten salt battery project aimed at strengthening long-duration renewable energy storage. The system, developed through a collaboration between Danish thermal energy storage firm Hyme Energy and Swiss engineering company Sulzer, is designed to supply electricity to as many as 100,000 homes for approximately 10 hours while achieving efficiency levels of up to 90 percent.

How Does the Technology Work

The molten salt battery operates by converting electricity into heat, raising the temperature of the salt to around 600 degrees Celsius. The stored thermal energy can later be converted back into electricity or used directly for industrial heat applications, offering flexibility across multiple energy use cases.

Unlike conventional battery technologies that store energy electrochemically, the system relies on thermal storage. This approach is particularly suited for long-duration storage requirements, where maintaining energy over extended periods is critical for balancing variable renewable generation.

Using Molten Hydroxide Salt to Store Energy for 2 Weeks

The technology utilises molten hydroxide salt, a low-cost byproduct of chlorine production, as the storage medium. 

Energy generated from renewable sources is stored in the heated salt using a two-tank configuration supported by proprietary corrosion-control technology.

The system can store electricity for up to two weeks. During charging, electricity is converted into heat, raising the salt’s temperature to approximately 600°C. During discharge, the hot salt is circulated through a steam generator that produces high-temperature steam.

This steam can be used directly in industrial processes or to drive turbines for electricity generation, positioning the technology as both a power and industrial decarbonisation solution.

Efficiency and Industrial Applications

The system achieves efficiency of around 90 percent for industrial heat applications and between 80 percent and 90 percent in co-generation scenarios. When used solely for electricity generation, efficiency is estimated at about 40 percent.

The launch reflects broader momentum behind long-duration storage solutions that can complement intermittent renewable energy sources such as solar and wind. By enabling energy to be stored for days or even weeks, molten salt technologies are emerging as a potential alternative to conventional battery storage for grid stability and industrial energy needs.