December 5, 2021

Salt breakthrough could halve the cost of storing solar energy

Danish startup accidentally developed the solution while working on nuclear research

Mimi Billing

4 min read

The team at nuclear startup Seaborg found out that their research findings could be used for renewable energy storage. Photo: Seaborg

One of the biggest difficulties with wind or solar energy is finding a good way to store it. Lithium-ion batteries are too expensive and need frequent replacing. Molten salt is a more efficient solution — but it tends to be better for storing heat rather than power. If you want both heat and power — for a low price — there have been few good options. Until now.

Seaborg, a small next-generation nuclear startup based in Copenhagen, has discovered a better molten salt storage solution using sodium hydroxide. Hydroxides can contain more heat per salt unit, making it more efficient and reducing the amount of salt needed. It s also about 90% cheaper than the cost of the salts currently used.

“We can more than half the cost of thermal energy storage in one go. And that allows us to come to a stage where we think [our business] can be competitive without any subsidies,” says Ask Emil Løvschall-Jensen, cofounder of Seaborg.


“If we filled up a building the size of the Colosseum in Rome with the salt and heated it to 700 degrees, we would actually be able to supply all of Italy's entire population with heat and power for 10 hours,” says Løvschall-Jensen.

The discovery came as an unexpected byproduct of the work Seaborg was doing on creating small modular nuclear reactors. The startup was set up in 2014 to create compact nuclear reactors on barges, using salt as the component to make them safer than traditional nuclear power plants but also to store the energy.

If we filled up the Colosseum in Rome with the salt and heated it to 700 degrees, we would be able to supply Italy's entire population with heat and power for ten hours

The problem with salt is that it is corrosive and wears away the steel pipes and tanks used to hold it. Heated to super-high temperatures, the corrosion reactions are sped up even further. Sodium hydroxide isn’t generally used for molten salt nuclear reactors because it is so corrosive, but Seaborg developed a method of controlling its corrosive properties.

The key technology enabler here is the chemistry control that limits the corrosion of structural materials in contact with the molten salt. The chemistry control is developed by Seaborg and is the core IP of the company.

But then they realised that it could be used for energy storage, especially for fluctuating wind and solar.

The discovery put them in a dilemma — which project to focus on?

“Somewhat counterintuitively, a breakthrough like this puts us in a pickle. On one hand, we cannot let it defocus Seaborg’s current mission to power regions with poor or no access to renewable energy sources through our compact molten salt reactor. But we also cannot simply shelve an opportunity to aid countries with access to renewables in accelerating this deployment,” Seaborg’s cofounder and chief executive Troels Schönfeldt says.

The founders of Seaborg decided to spin off the energy storage solution to a sister company, Hyme, with Løvschall-Jensen as the chief executive. Seaborg’s current investors helped raise around €10m to take the findings to the demonstration phase, due in 18 months.

I have three kids and I want to go home to them and say that we are actually doing something [to save the planet]

The good news is, it might help Seaborg start to see revenues earlier than a nuclear startup would normally expect. The first commercially built facility is expected to be ready for operational use within three years. For a deeptech startup in the nuclear space, that's a short timeframe.

“This is going to be an opportunity to actually accelerate the use of some of the technology we've developed in other areas. And I like that we can get it out. That thrills me,” Løvschall-Jensen says

He adds jokingly: “ I have three kids and I want to go home to them and say that we are actually doing something [to save the planet]”


Løvschall-Jensen says storage solutions like these will help in the transition to sustainable energy, especially for industry and manufacturing, which are heavily reliant on energy 24/7 and use gas or fossil sources to cover their needs.

“To make that transition, we need thermal energy storage solutions since you cannot rely on intermittent sources of electricity directly. Those prices would be too high. So instead, you really need something that can store it. And that is why salt is a gamechanger,” Løvschall-Jensen says.

Mimi Billing

Mimi Billing is Sifted's Europe editor. She covers the Nordics and healthtech, and can be found on X and LinkedIn