Energy provider Flexbase has commenced construction on what will become the world’s largest battery energy storage system (BESS) in Laufenburg, Switzerland.

The Laufenburg Technology Center in the northern canton of Aargau will house a redox flow BESS facility with an eventual battery capacity of 1.6GW and a storage capacity of 2.1GWh.

The site will also host a 480MW AI data center. Construction will be overseen by the Swiss firm Erne and is scheduled to be completed by 2029, with total costs estimated to be between 1 billion to 5.5 billion CHF ($1.27bn-$7bn). DCD has approached Flexbase for comment.

The Laufenburg Technology Center will be situated near the ‘Star of Laufenburg,’ a substation that serves as an interconnection hub for the Swiss and wider European electricity grids.

By connecting to this facility, Flexbase said in 2024, “this allows the battery storage system to reach its maximum potential by contributing optimally to national and international grid stability, while at the same time minimising power transmission losses.”

Redox flow BESS facilities store energy in liquid electrolytes in two separate tanks, in which electrochemical reactions can be stimulated to absorb or discharge electricity.

Advocates for the technology argue that its safety and scalability are superior to those of its lithium-ion equivalent, as the system is non-flammable and its expansion is only contingent on the construction of larger liquid tanks.

At Laufenburg, construction is underway on excavation pits almost 30 meters (98ft) deep to accommodate the huge BESS planned by Flexbase. The firm claims that the facility’s redox flow batteries will eventually be capable of supplying electricity to up to 210,000 households for a full day.

The site will also house a large data center. Billed by Flexbase as Switzerland’s “first sovereign AI factory,” the firm previously stated that the facility would occupy 600 sqm (6,500 sq ft), incorporate a liquid cooling system, and be at least 30 meters high to accommodate a waste heat system. However, according to Südkurier, the construction of that system will now be delayed until 2029.

The Laufenburg Technology Center was originally proposed as part of several network-wide upgrades to Switzerland’s electricity grid, as it prepares for greater supply from several new renewable power installations across the country and higher levels of demand.

Much of the latter is anticipated to come from new data center projects, with analysis published in the Zürcher Oberländer last year concluding that the sector’s power needs grew from 2.1 to 4 terawatt hours between 2019 and 2024. The data center market in Aargau itself, however, remains small, with only two facilities run by the operator Green.

Learn more about the data center market in Switzerland and the wider DACH region, and meet with other executives and experts at the DCN Zurich event later this year.