Wien Energie has put a redox flow battery into operation at the site of its Donaustadt power plant in Vienna. It is the utility's first battery storage system using a water-based electrolyte, and at 80 kW of power and 230 kWh of capacity it is currently the largest operating storage system of its type in Austria.
Anatomy of the pilot
The system is housed in a 25-tonne 20-foot container, with the electrolyte stored modularly in two tanks. The hardware comes from European manufacturer Invinity Energy Systems in cooperation with Lower Austrian company Wildburger Power & Storage; Invinity CEO Jonathan Marren said the project demonstrates the strengths of vanadium redox flow batteries in practical operation.
The core design difference matters. Unlike lithium-ion batteries, redox flow systems store energy in a non-flammable liquid electrolyte — largely water — held in separate tanks rather than in the cells themselves. That architecture is what makes them suited to storing larger amounts of energy over several hours, and it is why they are designed for a high number of charge cycles and a long operating life. The vanadium itself is not consumed and can be recovered and reused at end of life, a circularity advantage lithium chemistries do not yet match.
Safety and siting advantages
Because the electrolyte is water-based, the technology is suitable for sites with high safety requirements such as power plant locations — precisely the constraint that shaped this deployment. The pilot stores surplus solar power from the adjacent photovoltaic plant and makes the energy available when needed.
One technology in a deliberate mix
Wien Energie is using the pilot to examine what role redox flow technology could play in its future storage mix. Its current portfolio already includes conventional lithium-ion large-scale battery storage as well as Austria's largest second-life battery storage system, built from retired electric vehicle batteries.
A secure and independent energy system needs powerful storage solutions alongside renewable expansion — which is why we deliberately rely on different technologies.
— Sascha Zabransky, Managing Director, Wien Energie (as reported by ELEKTROPRAXIS)
At 230 kWh, the Donaustadt unit is a pilot, not a power asset. But it is a meaningful data point for the LDES sector: a municipal utility with real lithium experience is testing flow batteries on an operating generation site, and doing so with European-supplied hardware. The operating data that comes out of Vienna will inform how far redox flow can scale in urban district and plant-level applications where fire risk and cycle life weigh more heavily than energy density.
This article was assisted by AI analysis. Please refer to the original source for official information.