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One year since winning Offshore Wind Innovators Awards

Elestor covered by TKI Offshore Energy: "How's Elestor faring, one year after winning both the Offshore Wind Innovators Jury and Audience Awards? We have a look at the innovators of renewable energy storage and the progress they made. Elestor offers an important element for a successful energy transition."

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Elestor secures top international scientists for its Technical Advisory Board

Arnhem, The Netherlands, May 21, 2024. Dutch long-duration electricity storage company Elestor has secured the participation of a prominent group of scientists and sector experts as members of its newly created Technical Advisory Board. “As a cutting edge technology company, we invest significant resources in research and development in order to ensure we remain ahead of rivals in the clean energy storage sphere,” said Guido Dalessi, CEO, Elestor. “This leadership position has enabled us to attract top international scientists to our Technical Advisory Board, which is obviously going to be 100% independent to preserve the integrity of its members and of their conclusions.”

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LDES: Hydrogen Flow Batteries with Guido Dalessi, CEO Elestor

For this podcast episode, we have a special guest, Guido Dalessi, CEO of Elestor. Listen as we delve into their unique Hydrogen-Bromine flow batteries, discuss LDES in the Europe, how to secure right partnerships, and Elestor's plans for growth. Kudos to {antokrator !

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An grid-connected energy storage system using Elestor technology.

Vakbeurs Energie 2024

Meet Elestor to discover how a unique energy-saving technology will deliver a sustainable, 100% carbon free energy system: Large-scale, long-duration, scalable and affordable

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The Business Booster (TBB)

Creating the future of sustainable energy today! The Business Booster is EIT InnoEnergy’s annual two-day international networking event that showcases 150+ sustainable energy technologies under one roof. Join us in 2024!

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Past events

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Sustainable Electrical Energy Centre of Expertise

Join Elestor CEO Guido Dalessi’s exploration of the power of innovative technologies.

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ReCharge Earth, Conference & Expo

See Elestor’s exhibit and hear our CEO Guido Dalessi explain the link between innovation and growth.

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Wind Energy Technology Summit

Hear from Elestor during day two: Production of green electrons & molecules at sea.

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Long-term performance of hydrogen-bromine flow batteries using single-layered and multi-layered wire-electrospun SPEEK/PFSA/PVDF membranes

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Sanaz Abbasiab, Yohanes Antonius Hugob, Zandrie Bornemanac, Wiebrand Koutb and Kitty Nijmeijer*ac
aMembrane Materials and Processes, Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands. E-mail:
bElestor BV P.O. Box 882, 6800 AW Arnhem, The Netherlands
cDutch Institute for Fundamental Energy Research (DIFFER), P.O. Box 6336, 5600 HH Eindhoven, The Netherlands


Sulfonated poly (ether ketone) (SPEEK), perfluorosulfonic acid (PFSA), and polyvinylidene fluoride (PVDF) were wire-electrospun. Subsequently, multiple electrospun layers in different arrangements were hot-pressed into sustainable membranes for use in hydrogen-bromine flow batteries (HBFBs). The relationship between the electrospun layer composition and arrangement, membrane properties, and battery performance was explored. Wire-electrospinning and hot-pressing improved SPEEK and PFSA/PVDF compatibility, yielding dense membranes. Higher SPEEK contents lead to rougher morphologies, while the insulating nature of PVDF decreases the ion exchange capacity (IEC) and HBr uptake compared to commercial PFSA. The multi-layer assembly negatively impacted the membrane transport properties compared to the single-layer arrangement. Although wire-electrospinning improves the polymer dispersion and fixed charge density, SPEEK-rich regions of the blend membranes lack the high selectivity of PFSA, thus reducing the ionic conductivity. This is especially clear in the multi-layer membranes with accumulated SPEEK in the intermediate layer in the through-plane direction. Following initial property comparisons, thinner wire-electrospun SPEEK membranes were prepared with area resistance in the PFSA-comparable range. Among the wire-electrospun SPEEK/PFSA/PVDF membranes, the single-layered membrane with 8 wt% SPEEK (SPF1-8; 62 μm) displayed stable HBFB performance at 200 mA cm−2 over 100 cycles (64 cm2 active area). Based on the ex-situ measurements and cell performance results, a total of ∼10.5 wt% SPEEK is suggested as the limit for both single and multi-layered wire-electrospun membranes, combined with a maximum membrane thickness of ∼50 μm. This ensures robust HBFB performance, positioning wire-electrospun SPEEK/PFSA/PVDF membranes as a PFSA alternative in energy storage.

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Wire based electrospun composite short side chain perfluorosulfonic acid/ polyvinylidene fluoride membranes for hydrogen-bromine flow batteries

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Yohanes Antonius Hugo a, b, Wiebrand Kout b, Antoni Forner-Cuenca a, Zandrie Borneman a, c, Kitty Nijmeijer a, c, *
a Membrane Materials and Processes, Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, PO Box 513, 5600MB Eindhoven, the Netherlands
b Elestor B.V., 6827 AV Arnhem, the Netherlands
c Dutch Institute for Fundamental Energy Research (DIFFER), P.O. Box 6336, 5600 HH Eindhoven, the Netherlands
⁎ Corresponding author. E-mail address: (K. Nijmeijer).


A main component of a hydrogen-bromine flow battery (HBFB) is the ion exchange membrane. Available membranes have a trade-off between the major requirements: high proton conductivity, low bromine species crossover, and high mechanical and chemical stability. To overcome this, electrospinning of a highly proton conductive polymer (short side chain perfluorosulfonic acid (SSC PFSA)) and a hydrophobic inert polymer (polyvinylidene fluoride (PVDF)) was used to electrospin composite polymer fiber mats. Piles of multiple mats were hot pressed resulting in dense ion exchange membranes. Membranes with three different SSC PFSA/PVDF ratios were prepared, characterized, and subjected to short and long term (1500 h) HBFB testing. The electrospun membranes have performances very comparable to those of commercial membranes. For the SSC PFSA/PVDF electrospun membrane, a higher SSC PFSA loading gives a higher membrane proton conductivity compared to a lower loading, but at the expense of a higher bromine species crossover. The SSC PFSA/PVDF (50/50 wt%) membrane shows a coulombic efficiency of 98%, a voltaic efficiency of 80% and an initial available capacity of 105 Ah L− 1 at a current density of 150 mA cm− 2, which equals that of the current benchmark long side chain PFSA membrane. This performance is constant over 200 cycles during 2 months of continuous HBFB operation.

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High selectivity-conductivity reinforced perfluorosulfonic acid membranes for hydrogen-bromine flow batteries.

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Yohanes Hugo1, 2, Wiebrand Kout1, Friso Sikkema1, Zandrie Borneman2, Kitty Nijmeijer2
1Elestor B.V., 6812 AR Arnhem, the Netherlands
2Membrane Materials and Processes, Eindhoven University of Technology, Department of Chemical Engineering and Chemistry, PO box 513, 5600 MB Eindhoven, The Netherlands


Reinforced proton exchange membrane (PEM) were developed to increase the mechanical strength of thin membranes (≤30 µm) for PEM fuel cell applications. In hydrogen-bromine flow batteries (HBFBs), Br2 and Br crossover through the membrane may affect the lifetime of HBFBs as a result of dissolution or passivation of the platinum catalyst. One study suggested that the reinforcement reduces the bulk Br2 and Br transport and x-y (in-plane) swelling [1].

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