Anthony Price reports from the International Flow Battery Forum in Vienna, where he finds an industry ready to meet the challenges of long-duration energy storage, albeit not without the obligatory note of caution.
Kees van de Kerk, president of Flow Batteries Europe (FBE), opening this year’s edition of the International Flow Battery Forum was clear: “The flow battery sector has been on a rollercoaster ride over the last few years” referring to the waves of optimism and pessimism that have cast their shadow over the industry. But, he declared, “we have reached the inflection point. The market is there, and we must now work together to make flow batteries cost-effective and scalable.”
As president of FBE, van de Kerk has a finger on the pulse of the industry. He invited Jonathan Marron of Invinity Energy Systems on to the stage to make an unscripted announcement on the indicative statements of intent for the long duration energy storage capacity market auction in Great Britain.
Invinity was brimming with pride as nine UK developers have selected its flow battery for the LDES cap-and-floor bids. To back up FBE’s claim that the market is there, Marron said that developers are not questioning vanadium flow battery technology, it is now seen as a mature business.
Flow Battery Forum returns to birthplace
The 2025 edition of the IFBF was held in Vienna, returning to where it was born in 2010. Once again, Cellcube, based just outside the city, hosted the event, with a visit to the company’s works at the end of the conference. But, along with many other flow battery manufacturers, Cellcube had lots to say.
Christoph Stelzer, CEO, has a clear mission: to deliver happy customers. Customers ask him, “Can we rely on you?” to which the answer was clearly “yes”, and this is proven in the delivery of real projects.
The pervading comment throughout the conference was that the role of long duration energy storage (LDES) is not widely understood – the simple energy storage message is well known, but the underlying need for deploying LDES is still unclear. Many current energy markets are distorted, favouring deployment of short duration frequency services with high value revenues in preference to LDES.
California greening
David Hochschild, chair of the California Energy Commission (CEC), is a true believer in the value of clean and green technologies. LDES is high on his agenda, and the CEC has been pushing ahead for clean energy. Despite recent changes in Washington, DC, the administration in the state of California is still committed to a sustainable energy future.
On the day of the conference, two-thirds of California’s electricity was derived from clean sources, 96% of capacity additions in the past year were clean, and 16GW of new energy storage has been deployed. The CEC has defined LDES to have an energy capacity of between eight hours and 100h and the CEC chair gave several examples of LDES deployments, including flow batteries across a range of applications.
Pumped hydro and batteries
At a local level, Lara Ottendorfer of the Austrian Ministry of Economic Affairs, Energy, and Tourism gave a top-level view of energy storage in Austria – naturally pumped hydro storage is high on the list. 88% of Austria’s electricity comes from renewable energy sources, making it the leader in the EU. But there are still underlying issues for batteries, including flow batteries in Austria. The new Electricity Industry Act will introduce reforms to promote system friendly behaviour and will remove the anomaly that pumped hydro is exempt from system charges, but batteries are not.
Lobbying for storage
Viktor Horváth, deputy state secretary for the Energy Transition of Hungary provided a useful insight into the energy structure of Austria’s neighbour. Hungary has seen the highest rate of growth of PV in Europe since 2019. There has been a major support scheme with 440MW of energy storage deployed in Hungary, including six flow battery projects totalling 33MW and 143MWH.
At a national level, Hungary offers companies low corporation tax and low income tax rates, and it already has a big battery industry, with 300GWh battery cell manufacturing due online by 2030. The plea to the flow battery community was that the lithium-ion industry is lobbying hard in Hungary, but where are you?
The representatives of Austria, Hungary and California discussed whether it was mandates, markets or subsidies that would make the difference to the flow battery industry Hochschild was firmly of the opinion that setting storage targets help – they set objectives for the market and this should be backed up by long term policies, such as a 25 year plan. In Hungary, with high electricity price peaks and high intraday spot prices, making the markets work improves bankability of projects and hence encourages investment.
Hunger for power
The market for energy storage is still relatively new. Even 10 years ago, a battery of 50MW would have been a significant investment, and potentially high risk. Pascal Wyss, representing FlexBase, a Swiss company based in Laufenburg, has started construction on the foundations for a 500MW multi hour flow battery, to be incorporated into a new data centre.
The flow battery will be 25 metres below ground, feeding an energy hungry bank of computing power sitting above it. Maintainability, reliability, sustainability and fire safety are essential attributes. With projects of this magnitude underway, the claim that the rollercoaster ride is over is justified – it should be just downhill from here.
Finding the sweet spot
FlexBase is a keen potential user of flow batteries, but there are many flow battery manufacturers competing to supply. Rongke Power from Dalian, in China, has installed 3.4GWh of flow batteries in its home territory. Philip Krause said that his customers viewed the vanadium flow battery technology as proven and reliable. The technology was bankable, and Rongke Power is now opening a business in Germany to supply the European market. All that is needed is to identify the sweet spot for each customer.
Verbund (the large Austrian energy business) and Electricite de Portugal (EDP) both provided an insight into their approaches to energy storage. Karl Anton Zach from Verbund pointed out the elephant in the room, – an 86% cost reduction in the cell price of lithium-ion batteries was a significant challenge for the flow battery industry.
Clearly, the market still favours investment in short term flexibility, however, he pointed out that for many applications linked with renewable energy charging power is more relevant than discharging power, and that charging efficiency has a direct linear effect on integration with renewables.
Christian Barba Rodulfo of EDP Renewables reported on three flow battery projects in EDP’s portfolio. In response to a question about the future of vanadium flow batteries, he referred to the need to present the business cases and the mode of operation of each asset.
Storage scaled for net zero
Richard Campbell, from the UK government’s Department of Energy Security and Net Zero reminded delegates of the UK’s storage at scale programme, with flow batteries represented in both streams – Invinity in stream 1, and Stor-Tera in stream 2. This storage at scale programme was the first major LDES initiative in the UK for more than 40 years. Keenly awaited by many, the cap-and-floor capacity auction had 171 applications, and DESNZ was expected to make the interim awards public by the end of 2025, with announcement of the final awards by Q2, 2026.
The UK was well represented at the IFBF, with Andrew Deadman of the Faraday Institution explaining that the UK would need 25TWh of new energy storage by 2050. The Faraday Institution would be issuing an open call in March 2026 for novel but viable technologies for long duration storage.
Cosmopolitan contributions
The international flavour of the IFBF was shown by the wide range of speakers from around the world, and the number of companies in the exhibition area.
There is much happening in Australia – Professor Jens Noack assembled a panel of experts reviewing recent projects, mainly in Queensland, but also touched on the wide range of flow battery companies on the other side of the world.
There were flow battery projects in Singapore, India, Spain and Ukraine. Aramco (Saudi Arabia) has developed a novel flow battery based on the vanadium iron system, which was particularly suited to the high ambient temperatures of the middle east.
Svetlana Novikova from the RDI Center in Tajikistan spoke enthusiastically about the potential for flow batteries in central Asia, and the development of vanadium resources in the country.
There is no shortage of vanadium, vanadium prices may be volatile, and many said that whilst predicting the forward price is a fool’s game, the vanadium supply industry is ready to respond to meet demand, and this does not place a limit on its use for energy storage.
Optimism with a cautionary note
The overview of the flow battery industry was rightly optimistic, with only a few words of caution in the way of progress.
There was disappointing news from Johannes Häntschel of Prolux, as Prolux is discontinuing its offering of a domestic flow battery for the German, Austrian and Swiss markets. There was also further disappointing information from Andreas Podias, a consultant with independent company TNO reporting on the 75kW/500kWh iron flow battery installed at Schiphol Airport which had been operational for just over a year and achieved very low efficiency.
Unfortunately there was no one from the flow battery manufacturer present to offer an explanation. But there was optimism from the market projections of market research company IDTechEx and considerable market growth is expected.
Mike Perry, of Storion Energy, a new company formed from Stryten Energy and Largo Clean Energy, explained its new flow battery offer, and gave pricing and performance indications. Storion has a continuous process for producing high purity electrolyte and, with a lease arrangement for the vanadium content, it is able to offer a whole system cost for a battery energy storage system at a lower cost than a comparable LFP system.
Flow batteries are much more than vanadium and there was news about other flow battery chemistries. Eugene Beh of Quino Energy provided useful updates on the progress with the company’s organic flow battery system. It is now able to produce organic electrolyte in a continuous flow process, achieving 150 tons/year, with an electrolyte cost target of $40–$45/kWh.
Organic developments
Delegate interaction at the IFBF is always high – in-session voting uses simple red and green signs, and Thomas Guarr of Jolt Energy used the voting cards to good effect, to ask delegates’ views on organic systems.
Although many showed scepticism about the future role of organics, he reminded us that organic LED’s are now commonplace in display screens, yet only a few years ago these too were treated with cynical disapproval. So be prepared for some major shifts in technology.
Of course, organics includes a very wide range of chemistries, and with a lot of detail from all the different manufacturers and researchers, these international gatherings are essential for networking and reviewing the status and potential of these newly emerging systems. It’s not just getting the technology right – the commercial aspects and raising and using finance is critical.
The overall business stories are fascinating. Allegro Energy from Queensland, Australia, is developing a microemulsion-based flow battery. The microemulsions avoid hydrogen or oxygen evolution, and their chemistry has a high cell voltage of 3.5V with a current density of 100mA/cm2. These metrics are dream figures for flow battery developers and we will be keenly waiting for the next report at IFBF 2026 on the demonstration at the Eraring power station.
Lifecycle analysis
The mix of sessions included discussion on manufacturing – not just factory processes, but also how to produce better materials to improve overall performance. As well as making flow batteries, the industry is also concerned about the whole life-cycle, and the potential for reusing materials and components.
It was interesting to hear from James Han of ACM Tokyo about using already recycled materials in carbon electrodes. It is easy to overlook the significant supply of carbon fibres available from the recycling of aircraft – but this high-quality feedstock is ideal, and ACM is now producing and testing electrodes from used aerospace components.
Aligned with a short talk on aerospace materials, we were also fascinated to hear Jan Girschik of Fraunhofer ICT explain how flow batteries could be deployed on the next generation of spacecraft as he summarised his work on the SPACEFLOW project with the German Space Agency.
Next year in Budapest
Before departing for a site visit to CellCube, delegates heard from several flow battery users: Michael Weixelbraun of Energie Burgenland, a local power supply company, explaining how and why local energy storage is essential for delivering customer service more efficiently. Philippe Stevens from EDF reported on the company’s successful trials with flow batteries and György Czipó from Ideona ZRT, based in Hungary, described its new projects, supported by EU funding to use flow batteries to improve renewables integration. The next IFBF will take place in Budapest, Hungary allowing participants to visit some of the recent local VFB projects.
The need for diversity
The final discussions, led by Patrick Clerens, director of the IFBF, summed up the very buoyant mood of the industry, but of course, there were elements of the tough road ahead. There is a need for diversity in the energy storage industry and flow batteries can provide a significant part of the deployed storage assets. Collaboration between companies, including up and down the value chain, is improving and there is now plenty of interest from investors and customers.
Van de Kerk, in his role as FBE President reiterated his call for action: requesting the European Commission and other governments to give at least the same support to flow batteries as other technologies, to bring in policies such as the UK cap-and-floor mechanism to encourage sensible investment in long-duration storage and he told the industry to work with FBE to get the technology on the front page, improve performance, reduce costs and take advantage now of the new markets that are opening up.
