The technology centre on the Swiss side of Laufenburg on the Rhine is set to house the world’s largest battery storage facility, according to plans drawn up by local companies. This innovative storage technology is safer than conventional systems and also excels in sustainability.

Laufenburg on the High Rhine straddles both Germany and Switzerland. In Laufenburg AG (Canton Aargau), south of the river, construction began in early May 2025 on an expansion of the local technology centre – commonly referred to as TZL. Among other facilities, the expansion will host an AI data centre, the world’s largest redox-flow (or flow) battery storage system – and a wind tunnel for research and development in sports engineering.

Sufficient buffer capacity for electricity trading

The primary function of the battery storage system – targeting a capacity of 1.6 gigawatt-hours (GWh) and an output of 800 megawatts (MW) – will be to purchase electricity for trading when prices on the power exchange are low, and to feed it back into the grid when prices rise. This will also support grid stability, voltage security, and reactive power compensation, the two project partners announced. They are the Aargau-based construction company Erne Group and Flexbase Group, a technology firm headquartered in Laufenburg, AG, as reported by Heise Online.

Battery and pumped-storage hydropower plants are becoming increasingly essential to harness volatile – but sometimes abundant – renewable energy from wind, solar, and hydro sources. Much of this energy is still literally lost underground, due to insufficient storage capacity and limited transmission infrastructure to move surplus power efficiently from northern to southern regions.

The world’s largest redox-flow battery storage facility currently operates in China, but offers only 400 megawatt-hours (MWh) of storage capacity and 100 MW of output – just one-eighth of the capacity planned for Laufenburg. A key advantage of such liquid-based batteries is their enhanced safety compared with other technologies, such as lithium-ion.

75% Water, 25% Vanadium

The planned battery storage system will consist of 75% water as the energy storage medium and 25% vanadium as the metallic electrolyte. According to a Flexbase company spokesperson, the targeted power and capacity figures “will certainly be met – and possibly even slightly exceeded.”

Flexbase estimates that the planned capacity will require 960 tanks – each with a diameter of three metres – and many millions of litres of electrolyte fluid. To accommodate this many tanks, the building must be correspondingly large.

Once completed, the facility will measure 180 metres in length and 78 metres in width; its height will reach 20 metres in the first phase and 30 metres in the second phase, with a depth of 25 metres. Today, the TZL site already hosts a kind of electricity hub for Central Europe – including the Laufenburg substation, affectionately dubbed the “Star of Laufenburg”, and the first European interconnected grid, established in 1958, linking Switzerland with its two neighbouring countries, Germany and France.