World’s Largest Redox-Flow Battery in Switzerland: Construction Progress on the Laufenburg Megaproject
Laufenburg (Switzerland) – In northern Switzerland, a Redox-Flow battery storage system of unprecedented scale is being built in Laufenburg. The storage facility is a central component of an integrated energy and technology campus that combines power infrastructure, data processing, and research at a single location.
Construction Progress After Swissgrid Approval: Redox-Flow Technology at Industrial Scale
On the site of the Laufenburg Technology Center (TZL) in northern Switzerland, construction is advancing for what is currently set to become the largest Redox-Flow battery in the world. The approved first expansion stage provides for a battery capacity of 800 MW and an energy storage capacity of 1.6 GWh. Plans envision an expansion to 1.2 GW and a capacity of 2.1 GWh. According to Flexbase, this stored energy could supply 210,000 households for a period of 24 hours.
Redox-Flow batteries differ fundamentally from conventional lithium-ion storage systems. Energy is stored in liquid electrolytes that circulate in separate tanks and react electrochemically across a membrane. Unlike lithium-ion batteries, Redox-Flow systems use an aqueous electrolyte. The liquid, which consists of 75% water, is therefore neither flammable nor explosive, can be expanded almost indefinitely, and is fully recyclable. This principle allows high cycle stability, good scalability, and a safe system due to the non-flammable medium.
Currently, excavation work is underway at the site for a construction pit nearly 30 meters deep, roughly the length of two soccer fields, which will house the central technical infrastructure of the storage system. The building will accommodate storage, pump, and system components of the Redox-Flow system. In parallel, an integrated technology complex with a data center, laboratories, and office spaces is being constructed.
According to Flexbase, the system can respond to charge and discharge demands within milliseconds, allowing it to feed large amounts of power into the grid or draw from it very quickly. The system is designed to absorb excess renewable energy and supply it again when needed. The aim is to support grid stability and enable the further expansion of renewable energy sources such as wind, hydro, and solar power.
The total investment for the project is estimated in media reports at over one billion US dollars. Operation is expected to begin in the late 2020s.
0.8 to 1.2 GW Storage Capacity – 1.6 to 2.1 GWh Energy Storage: Operational Context
Even the first expansion stage of the system with 800 MW capacity and 1.6 GWh storage allows for significant flexibility in the power system. Different operational scenarios can illustrate this. For example, at a discharge rate of 100 MW, the plant could theoretically supply energy for 16 hours. At 400 MW, the duration would be 4 hours, and at 800 MW, 2 hours.
In the planned final stage with 1.2 GW capacity and 2.1 GWh, much longer runtimes are possible depending on operational mode. If full capacity is drawn, the continuous discharge time would be around 1.75 hours.
The range of different consumption profiles highlights the system’s role as a short-term flexibility and balancing storage in the power grid: lower output allows for longer supply times, while high output can be used to cover peak demand and stabilize the grid.
This positions the project as an infrastructural link between volatile renewable generation and increasingly electrified demand. Particularly in combination with the growing electricity demand from data centers and industrial applications, the Laufenburg site could become a central flexibility hub in the European energy system.
Redox-Flow Storage in an International Context: Laufenburg Sets New Standards
Globally, Redox-Flow technology is currently transitioning from pilot applications to large-scale energy storage for the power system. While the largest existing installations, such as the Jimusaer storage (200 MW, 1 GWh) or the Dalian system (up to around 200 MW, 400–800 MWh), are located in China, many projects outside Asia are still in the range of a few tens to a few hundred megawatts.
In Europe and North America, planning and demonstration projects currently dominate, often focusing on grid stabilization and long-term storage. Against this backdrop, the Laufenburg project stands out: with a planned final capacity of 1.2 GW and 2.1 GWh, the system significantly surpasses previously known projects in the Redox-Flow segment and sets a new benchmark globally. This could shift the focus of technology development from individual projects to system-relevant large-scale storage that can be directly integrated into regional transmission networks and serve as an infrastructure component of the energy transition.
Source: IWR Online, 13 May 2026