In northern Switzerland, construction crews are digging a pit more than 27 meters deep and roughly the length of two soccer pitches. When they’re done, it will hold the world’s most powerful redox flow battery — a 2.1-gigawatt-hour storage system designed to stabilize Swiss and European power grids and power 210,000 homes for an entire day.
At a glance
- Redox flow battery: The FlexBase system will store 2.1 GWh of electricity in liquid electrolytes — significantly larger than China’s 700-MWh Xinhua Ushi project, currently the world’s biggest operational system of this type.
- Grid-scale energy storage: The battery can inject or absorb up to 1.2 GWh in milliseconds, matching the output of the nearby Leibstadt nuclear power plant, and will be charged primarily by excess wind energy.
- FlexBase technology complex: The project, costing over one billion dollars, is set to be completed by 2029 and will anchor a 20,000-square-meter site that also includes a data center, labs, and offices.
Why this battery is different
Most people picture lithium-ion when they think of batteries — the kind in phones, laptops, and electric cars. Those are excellent for short bursts of storage. But grids need something different: the ability to hold large amounts of energy for hours or days and release it on demand.
Redox flow batteries do exactly that. Two liquid electrolytes are stored in large tanks and pumped through a cell divided by a membrane. When charging, ions cross the membrane and change oxidation state, locking energy into the liquid. When discharging, the process reverses. The cycle can repeat indefinitely without degrading the system.
The result is a battery with a practically unlimited lifespan. It’s also non-flammable and almost entirely recyclable — two attributes that lithium-ion systems can’t claim.
Old science, new urgency
The chemistry behind redox flow technology dates to 1879. NASA refined it through research programs in the 1950s through 1970s, but for decades it remained too expensive for commercial deployment at scale.
That’s changed. As the industry has matured, the cost of key components — tanks, membranes, cell stacks, and pumps — has dropped considerably. FlexBase co-founder Marcel Aumer told Swiss public broadcaster RTS that the system will respond to grid fluctuations within milliseconds, a speed that makes it valuable for balancing supply and demand in real time.
Switzerland isn’t alone in betting on this technology. Japan, Germany, and China have all made significant investments in redox flow storage, and the global market is expanding rapidly as renewable energy penetration deepens and grid reliability becomes a bigger concern.
Powering an AI-hungry grid
The FlexBase battery has a specific local purpose beyond general grid support. The region around the construction site is seeing surging electricity demand from AI data centers — facilities that draw enormous, continuous power loads. A storage system of this scale can absorb surplus renewable energy when production is high and release it precisely when those data centers need it most.
That dual role — grid stabilizer and on-demand industrial power source — reflects a broader shift in how engineers are thinking about large-scale energy storage. It’s no longer just about backup power. It’s about making variable renewables reliable enough to replace firm generation.
What’s still ahead
The battery isn’t expected to come online until 2029, and large infrastructure projects of this complexity routinely face delays and cost overruns. The electrolyte chemistry, while stable, also requires careful handling and long-term maintenance that will need to be proven at this unprecedented scale.
Still, the excavation now underway in northern Switzerland represents a tangible step toward the kind of storage infrastructure that clean energy grids will require. The technology is old. The ambition is new. And the pit in the ground is real.
Read more
For more on this story, see: New Atlas
For more from Good News for Humankind, see:
- Renewables now make up at least 49% of global power capacity
- Marie-Louise Eta becomes the first female head coach in men’s top-flight European football
- The Good News for Humankind archive on renewable energy
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