Switzerland’s Giant Redox-Flow Battery Could Change Grid Storage

Switzerland's Giant Redox-Flow Battery Could Change Grid Storage

Switzerland is building what developer FlexBase claims will be the world's most powerful redox-flow battery in Laufenburg, canton Aargau — a system designed to inject or absorb up to 1.2 gigawatts of electricity within milliseconds, equivalent to the output of the nearby Leibstadt nuclear plant.

The project is notable not just for its scale, but for what it represents. As solar and wind power take on a larger role in the energy mix, grids need storage systems that can absorb surplus power and release it quickly when demand spikes. That is exactly the kind of job redox-flow batteries are designed to do.

Key facts at a glance

Detail Value Location Laufenburg, canton Aargau Developer FlexBase Capacity Up to 1.2 GW (injection/absorption) Response time A few milliseconds Excavation 27-metre-deep pit, longer than two football pitches Technology campus 20,000 m² — AI data centre, offices, labs Estimated cost CHF 1–5 billion (~$1.2–6.2B), privately financed Jobs expected ~300 Target operation 2029 Grid connection Swissgrid — first direct national grid connection in Switzerland Unlike lithium-ion batteries, which store energy in solid electrodes, redox-flow systems keep energy in liquid electrolytes held in large tanks. When electricity is needed, the liquids are pumped through cell stacks that convert the stored chemical energy back into power. That architecture makes them well-suited for large-scale, stationary storage.

FlexBase co-founder Marcel Aumer has described the system's millisecond response time as a key differentiator for grid-balancing applications. The site is being developed as part of the Laufenburg Technology Centre, a 20,000 m² campus that would also include an AI data centre, offices, and laboratories, creating around 300 jobs.

Swissgrid, operator of Switzerland's national high-voltage network, plans to connect directly to the Laufenburg site — a first for the country. Spokesperson Gabriele Crivelli described large batteries as "a key component of Switzerland's future grid network," pointing to growing demand for grid flexibility as renewables expand.

Not everyone is convinced redox-flow is the winning technology. ETH Zurich professor Tobias Schmidt, who co-authored a 2020 study on battery technology trajectories published in Joule, is openly sceptical: "I don't know the exact figures for Laufenburg. But I'm surprised. I wouldn't invest in this technology." His 2025 follow-up in Nature Energy found that sodium-ion batteries inherit the steep learning curve of lithium-ion, making metal-ion systems "really hard to beat" on cost and scale. Aumer himself acknowledged Europe's position: Japan, China, and South Korea are roughly seven years ahead of Europe in redox-flow deployment.

That debate matters, because the future of grid storage will likely be shaped by whichever technologies can improve most quickly and economically. Even so, projects like Laufenburg serve a purpose beyond their own commercial success — they push the market forward, prove what is possible at scale, and sharpen the competition among storage technologies.

Why it matters Large-scale battery storage is becoming critical infrastructure for the energy transition. As more renewables come online, the ability to store electricity and dispatch it within milliseconds will help smooth supply fluctuations, reduce outage risks, and support a more resilient grid. Switzerland's redox-flow project — the largest of its kind if completed as planned — offers a concrete test of whether that promise can be delivered at gigawatt scale by 2029.