Utility Vattenfall, steel-maker SSAB and iron mining company LKAB have started construction of a pilot-scale rock cavern in northern Sweden to store fossil-free hydrogen that will be another step towards the production of green steel.

Located in Svartöberge, the 100m3 storage facility being hollowed-out some 30 metres underground in Scandinavian bedrock will cost just over SKr250m ($29m), which is financed equally by the project partners along with the Swedish Energy Agency (SEA).

The hydrogen storage cavern, expected to be operational from 2022 to 2024, is part of the joint Hybrit initiative that last year already had started operations on what it claimed is the world’s first pilot plant dedicated to the production of fossil-free steel, in the northern Swedish town of Luleå.

"We're really pleased that Hybrit is continuing to lead the development of efficient production for fossil-free steel, as we're now also building a pilot storage facility for large-scale fossil-free hydrogen in Luleå,” said Hybrit chairman and head of strategy at Vattenfall Andreas Regnell.

“Storage provides the opportunity to vary demand for electricity and stabilise the energy system by producing hydrogen when there's a lot of electricity, for example in windy conditions, and to use stored hydrogen when the electricity system is under strain."

Vattenfall hasn’t spelled out whether the electricity to be used to produce the fossil-free hydrogen for Hybrit will come from renewable energy – wind or hydro – or nuclear power. The utility produces both in Sweden, but there is an increasing resistance in the EU (especially from countries like Germany or Austria) to label nuclear power as clean energy.

The hydrogen produced and stored at Svartöberget will be used in the plant’s direct reduction reactor to remove oxygen from iron ore pellets. The fossil-free sponge iron resulting from the process will then be used as a raw material to manufacture steel.

Building the storage facility underground provides opportunities to ensure the pressure required to store large amounts of energy in the form of hydrogen in a cost-effective way, Vattenfall explained.

"This is another important step, not just for us, but in the conversion of the entire industry. With Hybrit, we're also working together to develop the technology for storing hydrogen in an efficient way, which is key to being able to produce fossil-free sponge iron, the raw material for the fossil-free steel of the future,” said Lars Ydreskog, director of strategic projects at LKAB and member of the Hybrit board.

“LKAB will need to become Sweden's and perhaps Europe’s biggest hydrogen producer in the future, and this pilot project provides additional valuable knowledge for the continued work in creating the world’s first fossil-free value chain for the iron and steel industry.”

Efforts to produce steel using green hydrogen (made through electrolysis from renewables) have also emerged in other European countries such as Germany or Italy.

German steel-maker Thyssenkrupp, for example, jointly with utility RWE is exploring the use of hydrogen instead of coke and pulverised coal in the steel-making process.

Rival steelmaker Salzgitter last month has commissioned a €50m ($60m) wind-powered hydrogen project with compatriots E.ON-owned Avacon and Linde in a project called Salzgitter-WindH2, which also aims at decarbonising the steel industry.

And Danish utility Orsted last week has proposed to build a 1GW electrolyser by 2030 fed by 2GW North Sea offshore wind farm to supply major industries in Dutch-Belgian border region, among them steel giant Arcelor Mittal.