Denmark’s Molten Salt Battery Could Power 100,000 Homes — Energy Breakthrough!

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 innovative system marks a major leap forward in large-scale, long-duration energy storage.

Using industrial byproducts and ultra-efficient heat storage technology, the project showcases how nations can store renewable energy at grid scale—reliably, safely, and affordably.

The implications? Massive. This could be the key to solving intermittency issues in wind and solar, decarbonizing industry, and creating a cleaner, more resilient power grid.

What Is a Molten Salt Battery?

At its core, a molten salt battery is a type of thermal energy storage system. But unlike lithium-ion or solid-state batteries that store electricity as chemical energy, this system stores heat—specifically, in molten hydroxide salts heated to extremely high temperatures.

Here’s how it works:

Electricity from renewable sources (like wind or solar) is converted into heat.
That heat is used to raise the temperature of molten salt to around 600°C (1,112°F).
The hot salt is stored in a two-tank system—one for hot, one for cooler liquid.
When energy is needed, the heat is used to create steam, which either:
- Powers a turbine to generate electricity, or
- Is fed directly into industrial processes that require heat.

Denmark’s MOSS Project: Specs and Scale

The world-first installation, called the MOSS demonstrator plant, officially launched in April 2024 in Esbjerg, Denmark. It’s capable of:

Storing 1 GWh of energy—enough to supply 100,000 homes for 10 hours.
Delivering up to 90% efficiency for co-generation (heat + power).
Offering 40% electricity conversion efficiency alone, which still outperforms many thermal systems.
Operating with 2-week storage capacity, making it ideal for grid balancing.

This is not a proof of concept—it’s already operational and commercially viable.

Why Molten Salt? A Byproduct Turned Powerhouse

The key material in this battery is molten hydroxide salt, a low-cost and abundant byproduct of chlorine production. Denmark, like many industrial nations, generates tons of it every year.

Rather than treating it as waste, Hyme Energy found a way to use it as a clean, stable heat storage medium.

Benefits of molten hydroxide salt:

High heat capacity (stores more energy per volume).
Non-flammable and non-toxic.
Readily available, making it economically scalable.
Operates at extremely high temperatures, ideal for both power generation and industrial use.

How Efficient Is It?

Let’s look at the numbers.

When used to generate both heat and power (co-generation), the system achieves 80–90% energy efficiency.
When converting heat back into electricity alone, it maintains around 40% efficiency, which matches or exceeds many fossil-fuel-based systems.
With zero direct CO2 emissions, the environmental footprint is minimal.

This positions molten salt batteries as one of the most efficient and clean energy storage options in development today.

Two-Tank Design: The Secret to Storage Stability

One of the biggest challenges with thermal batteries is heat loss over time. Denmark’s molten salt battery tackles this with a two-tank system:

Hot Tank: Stores the high-temperature molten salt after it’s been heated using excess electricity.
Cold Tank: Holds the salt once it has transferred its heat during energy extraction.

Using advanced insulation and heat-retention technology, the system can store energy for up to two weeks with minimal loss—making it ideal for grid stability during seasonal dips in renewables.

Real-World Impact: Holstebro Facility and Industrial Use

Following the success of the MOSS demonstrator, Hyme is now building a 200 MWh molten salt plant in Holstebro, Denmark, which will:

Provide thermal energy to Arla Foods, one of Europe’s largest dairy producers.
Reduce Arla’s gas consumption by 50%, significantly cutting carbon emissions.
Save over €3 million ($3.1 million) annually in energy costs.
Help meet EU decarbonization targets for industrial sectors.

This project shows how molten salt energy isn’t just about electricity—it’s about clean, direct heat for sectors that account for over 20% of global CO2 emissions.

The Sulzer Partnership: Engineering at Scale

Sulzer, a global engineering powerhouse, plays a crucial role in enabling this battery’s performance. They provide:

High-efficiency molten salt pumps, capable of handling high temperatures and corrosive environments.
Thermal circulation technology to optimize salt flow and minimize energy loss.
Support for scaling the system to grid-level deployments around the world.

Advantages Over Lithium-Ion and Other Grid Batteries

While lithium-ion batteries dominate EVs and consumer devices, they’re not always ideal for grid storage. Here’s how molten salt stacks up:

Feature	Lithium-Ion	Molten Salt
Energy Storage	Electrical	Thermal
Duration	4–6 hours	10–336 hours
Efficiency	~85–90%	80–90% (heat) / 40% (electricity)
Cost per kWh	High	Low (uses byproducts)
Fire Risk	High	Very Low
Scalability	Moderate	High (modular tanks)
Environmental Impact	High mining, recycling issues	Low (recycled input)

For large, long-duration, low-cost storage, molten salt is rapidly proving to be a superior solution.

Decarbonizing Industry: A Hidden Superpower

Most people associate energy storage with electricity. But industry runs on heat.

Steel, cement, paper, food, and chemicals all require steam or process heat between 150°C and 800°C.
Today, this heat is often produced by natural gas or coal.
Molten salt batteries can deliver this same heat—cleanly and continuously.

This makes Denmark’s project one of the first real steps toward decarbonizing industrial heat at scale—something many climate models say is essential to meet global targets.

Global Replicability: Can Other Countries Do This?

Yes—and they should.

The beauty of molten salt storage is that it:

Doesn’t rely on rare materials.
Uses existing industrial infrastructure (tanks, steam pipes, pumps).
Is modular, meaning it can scale from a few MWh to multi-GWh systems.
Can be paired with solar, wind, or nuclear energy.

Any country with industrial salt byproducts or large-scale renewable energy can adopt this system. It’s especially viable in Europe, the U.S., China, and India.

Challenges and Next Steps

As with any emerging tech, molten salt storage faces some hurdles:

Upfront capital costs are still higher than traditional thermal systems.
Public and regulatory awareness is limited.
Long-term performance data is still being gathered.
Workforce training is needed to manage new systems safely.

That said, with the success of Denmark’s system, global interest is accelerating. Expect to see more announcements in Germany, the U.S., and Japan soon.