Hungary’s STS Group has presented its electricity-storage park at Balatonberény, south of Lake Balaton, whose core is a vanadium-redox flow battery with a nominal storage capacity of 10.8 MWh, the company said at an industry event on Tuesday, according to Economx.
The facility, handed over during the summer, was presented together with the Hungarian Machinery and Energy Association (MAGEOSZ). The 10.8 MWh the park can hold is equivalent to close to 2,000 households’ daily electricity consumption, the report says, and the investment was built with a HUF 2.16 billion grant from the European Union’s Recovery and Resilience Facility.
How flow batteries differ from lithium
A vanadium-redox flow battery stores energy in liquid electrolyte held in tanks rather than in solid cells, and pushes that liquid through a stack to charge or discharge. The trade-off is size and cost against duration: flow systems are well suited to storing surplus solar and wind output for several hours and cycling many times a day, which is the problem grid operators face as Hungary’s solar capacity grows.
STS brought in the UK-based Invinity Energy Systems, a specialist in grid-scale flow storage, to help build the park. Hungary already has smaller vanadium installations, at Sőpte in Vas county and Öskü in Veszprém county, with a combined capacity of 5.5 MWh.
Why the site moved
STS managing director Gyepes Balázs said the company began looking at storage seriously around 2017, when Hungary’s solar build-out became hard to miss, and weighed lithium-ion against molten-salt (NAS), compressed-air (CAES), pumped-hydro (PHS) and vanadium flow options. Planning issues led the company to move the project from its originally intended site at Sümeg to Balatonberény.
Part of a wider storage push
The Balatonberény park is one of a series of storage moves by the group. The utility ALTEO and SMEGSolar, part of the STS Group, signed a long-term cooperation agreement in January 2026 covering electricity-storage investments, according to ALTEO’s investor disclosure.
Storage is becoming the binding constraint on Hungary’s renewables expansion: solar output peaks in the middle of the day, and without storage or flexible demand that power is curtailed or pushes prices negative. The government has been funding grid-scale battery projects, and developers have been racing to add capacity alongside new solar plants.
Asked about the economics, STS executives said the company sees storage as a long-term business line and that Balatonberény is unlikely to be its last such investment. The Daily Lens could not independently verify the park’s performance data or the grant figures with Hungary’s energy ministry at the time of writing.
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