Molten salt as a battery: The world’s first facility of its kind will be operating in Denmark in a few years

The future facility will be located in Rønne Harbour on Bornholm. Illustration: Hyme

An old power station in Rønne on Bornholm is to be converted to store electricity from wind turbines and solar panels in molten salt of sodium hydroxide and be able to release the energy again as electricity and/or heat.

The new facility, which will be the first of its kind in the world, will have a storage capacity of approximately 20 MWh and an output of 1 MW.

According to the plan, it should be ready in the autumn of 2024.

The project owner is Bornholms Energi & Forsyning (BEOF), while the salt storage technology has been developed by Hyme, a spin-off company of Seaborg, which is working on developing a small, modular nuclear reactor.

“We are happy that Hyme, though the collaboration with Bornholms Energi & Forsyning, has the opportunity to show that our storage technology can supply power and heat efficiently as part of the sustainable CHP plants of the future,” Ask Emil Løvschall-Jensen, CEO of Hyme and co-founder of Seaborg, said to Ingeniøren.

The whole idea of Hyme’s technology is based on the fact that, in the future, there will be a need to store energy for when the weather is not sunny or windy, and that conversely there will be a need to be able to take over the energy from solar panels and wind turbines when “too much” electricity is produced to be sent to the grid.

In Hyme’s energy storage solution, this is achieved though the renewable power heating molten salt, sodium hydroxide (better known as caustic soda).

The energy can be stored in molten salt for 24 hours or longer with an energy loss of less than 1 percent per day, Hyme claims.

Reuse brings the price down

When the project on Bornholm is completed, Hyme expects to be able to deliver commercial facilities with a storage capacity of 1 GWh or more.

A facility of this size can supply enough electricity and heat for 200,000 inhabitants.

The technology has been developed to minimize costs, Ask Emil Løvschall-Jensen explains.

Hyme’s energy storage facility stores the energy in the molten salt of sodium hydroxide, which is pumped through a system to create steam that drives a turbine. Illustration: Hyme

“Our technology excels in being able to deliver steam at the temperatures that CHP plants normally use, and in doing so we can reuse their turbines—and a number of other equipment as well. This saves quite a bit of money, so our technology will be overall relatively cheap to build.”

The energy storage facility is part of a larger project called 2LIPP, worth around DKK 100 million, of which DKK 60 million is financed by the EU. The other storage technologies used in the project are a flywheel energy storage solution from Dutch company QuinteQ, a recycled lithium battery from Swedish company PLS Energy, and an energy management system from Swedish company Pini Solutions, which can run the three storage technologies simultaneously.

Conventional CHP plants can be retrofitted with thermal storage systems and continue to play an important role in stabilizing the grid. By “retrofitting” obsolete power plants, their boilers and steam turbines can be reused to reduce costs. Illustration: Hyme

The project consortium behind 2LIPP (2nd Life to Power Plants) sees enormous potential for future implementation of the technology in places where there are currently fossil and CHP plants.

When they are decommissioned, the power plants’ existing electrical infrastructure, boilers, and steam turbines can be utilized, points out David Tveit, director at the Danish Technological Institute, which is a partner in the project.

“The current energy crisis has shown us that the green transition must be accelerated. It will require expansion of the electricity grid to transport, produce, and store energy, which has already put Europe’s grid operators under pressure to keep up. With 2LIPP, we take advantage of the existing infrastructure for the expansion of energy storage and test methods to avoid major conversions of the grid and thus create a shortcut in the green transition,” he says.

The project’s partners also include Energy Cluster Denmark, Fraunhofer (research and development, Germany), Gdansk University of Technology, DTU, Euroheat & Power (international network for district heating), Netzgesellschaft Eisenberg (grid operator), University of Applied Sciences Jena, Koksik (Polish coal plant in Reda).