Sulzer, Hyme Energy to commercialize novel molten salt energy storage

Danish thermal energy storage developer Hyme Energy and Switzerland-based fluid engineering specialist Sulzer have joined hands to pave the way for the commercialization of their novel molten salt energy storage solution, a green alternative for industrial heat generation.

The two companies previously collaborated on the MOSS demonstrator plant project in Esbjerg, Denmark, inaugurated in April 2024, which proved the concept of storing renewable energy in molten salt at temperatures up to 600°C.

This innovative technology uses molten salt to store energy from renewables to deliver green heat for industrial processes. Captured energy is discharged when molten salt is pumped from a storage tank to a heat exchanger, producing steam for industrial use.

Sulzer played an important role by supplying critical pump technology that enables the controlled movement of molten salt within the system.

The Swiss manufacturer has been active in molten salt pump development for the last 20 years. In one of its previous projects, it supplied molten salt pumps for a 100 MW concentrated solar power (CSP) project in China, designed to provide solar power 24 hours a day. Its experience with Generation 3 CSP systems, proven molten salt pumps, and rapid prototyping will support Hyme Energy in commercializing its innovative energy storage technology.

“With the MOSS plant providing good results since its inauguration in April 2024, we’re now working with Hyme Energy to further optimize the system, improve the competitiveness of the solution and establish a strong supply chain,” said Benoît Martin, advance engineering manager at Sulzer.

Hyme’s technology

Hyme’s energy storage technology stores electricity from renewable sources in molten hydroxide salt for up to two weeks. It is based on a two-tank storage design developed for concentrated solar power (CSP) plants and Hyme’s proprietary hydroxide salt corrosion control technology.

When charging electricity from renewables is converted into heat through electrical heaters. Salt from the cold tank is circulated through the electrical resistance heaters and heated up to 600 C, then stored in the hot tank.

At the time of discharge, salt from the hot tank circulates to the steam generator, where the energy is transferred to water, generating high-temperature steam. Steam can be used directly in an industrial process or used to power a turbine and produce electricity and district heating. After that, the cooled salt is pumped back into the cold tank until the next charging cycle.

The efficiency of the storage system varies according to its use. For industrial heat, Hyme envisages efficiencies of around 90%, while for co-generation, the figure is somewhere between 80% and 90 %. For power generation alone, the company expects an efficiency of around 40%.

Hyme’s storage technology is scalable and a 1 GWh facility with sodium hydroxides should be able to produce power and heat for around 100,000 households for 10 hours of discharge, said the company.

Since sodium hydroxide can be produced at low cost from seawater as a byproduct of chlorine production, the company calculates that this is six times cheaper than standard salts used for storage.

Founded in 2021, Hyme is developing what is touted as the world’s biggest industrial thermal energy storage system. The 200 MWh site planned in Holstebro, Denmark, is projected to save Danish-Swedish dairy co-operative Arla Foods around €3 million ($3.1 million) per year on its process heat bills while generating extra revenue from providing grid stabilization services to Danish electricity transmission system operator Energinet.

“Our technology is designed to integrate with existing infrastructure, making adoption easier for industries looking to transition to sustainable energy. For us at Hyme, it is key to work with established partners like Sulzer. By combining our strengths, we can accelerate progress and bring this solution to market faster,” says Ask Emil Løvschall-Jensen, CEO and co-founder of Hyme Energy.