What can be understood by a flow battery?
Guido Dalessi: Flow batteries are a unique type of battery initially developed by NASA in the 1960s. It was not until the 1980s that they gained popularity in the industry after demonstrating the ability to withstand over 10,000 charge or discharge cycles.
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What is the focus of Elestor’s flow technology?
Our flow battery design is based on an electrochemical cell, where chemical energy is generated by a reaction between two active materials. In theory, a flow battery can be built using a variety of active materials, so-called redox couples. Elestor has developed several of these. At first, Elestor developed a hydrogen-bromine chemistry concept which is still considered the holy grail of chemical compounds. Minimizing the time to market, we already introduced the hydrogen and iron-sulfuric acid chemistry concept last year. We selected these chemicals to meet our goal of creating a storage system with the lowest possible storage cost per Mwh.
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Does the storage system encompass numerous components?
The active materials are separated by a membrane and circulate in a closed loop, each within its own compartment. Charging the battery triggers a chemical redox reaction, discharging reverses the reaction.
What is the advantage of this technology compared to lithium systems?
Flow batteries are ideal for long-duration energy storage as they are designed to economically deliver power for a minimum of eight hours to a few days. While other batteries can technically provide power for a similar amount of time, flow batteries are among the most cost-effective solutions for this purpose. In contrast, lithium batteries are more viable for short-duration applications. As the energy transition progresses, periods of renewable electricity shortages are becoming longer, lasting up to a several days. That’s where flow batteries come in.
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You say your technology can be integrated into electrolyzers and hydrogen infrastructure. How does this work?
To explain how hydrogen is integrated into our system, we need to take a closer look at the battery design: Each cell stack membrane in our storage systems has one side in contact with an aqueous solution of iron-sulfate, while the other side is in contact with a hydrogen circuit. The battery generates hydrogen during the charging process, essentially acting as an electrolyzer. In the stand-alone battery, the generated hydrogen is stored in a separate tank, as it is required for discharging.
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Does the battery consume hydrogen?
The battery does not consume hydrogen but utilizes hydrogen and iron-sulfate as active materials for charging and discharging. When the battery is discharged, the hydrogen becomes part of the electrolyte again. Rather than storing hydrogen in a large tank, we can connect the battery to a hydrogen pipeline. In this case, the battery feeds hydrogen into the pipeline when charging and extracts the same amount of hydrogen from the pipeline when discharging. This approach reduces both space requirements and capex, which in turn reduces the storage costs per Mwh.
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Does that mean that you are competing with the hydrogen industry?
On the contrary, we support the hydrogen industry by maximizing the utilization of electrolyzers. Our flow battery can significantly reduce the cost of green hydrogen production when integrated with electrolyzers. By supplying the electrolyzer with low-cost electricity, we help ensure a cost-effective 24/7 hydrogen production. This effectively bridges the perceived divide between the hydrogen and electricity infrastructures, which are often viewed as competing solutions rather than complementary parts of a unified system.
Are there other companies with the same or similar technologies?
As far as I know, we are the only company using this specific chemical compound of hydrogen and iron-sulfate. Our approach to integrating our flow battery with electrolyzers and connecting to pipelines is particularly unique.
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How does your technology reduce electricity storage costs?
The best time to charge the battery is when electricity prices are low, and discharge when the prices rise. The difference between these prices determines the margin per megawatt-hour. However, it is also essential to consider the storage costs for each megawatt-hour held in the battery – the lower this cost, the better the margin.
Normally redox flow batteries use vanadium. What is the economic advantage of your chemistry?
Many other flow battery manufacturers use vanadium as an active material – an example of how the choice of chemicals also impacts storage costs. While vanadium-based batteries have been on the market for about a decade and are highly reliable, the chemical is unfortunately expensive and its sources are limited. In contrast, iron-sulfate is abundant worldwide and is one of the most widely used chemicals in the industry. This widespread availability ensures that there will be no shortages or economic dependencies, keeping prices consistently low, even in the future.
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What markets are you focusing on?
Although we are based in the Netherlands, our primary focus extends beyond its borders as we seek opportunities that better match our goals. Additionally, the new right-wing government does not support the energy transition strongly enough. There are other European countries where our flow battery technology is likely to gain more traction than in the Netherlands.
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For instance?
To identify our best markets for adopting our flow technology, we conducted a detailed analysis of all European countries, evaluating over ten factors that influence how quickly this technology could be adopted. At this time, our top markets are the UK, Spain, Italy, and Germany, where we see the most immediate potential. Storage capacity will continue to increase and eventually last several days. With the ongoing advancements in our flow batteries, we are committed to helping accelerate the energy transition.
Interview by Heiko Schwarzburger.
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ees Innovation Hub
New area at Europe’s largest energy storage exhibition
Elestor will exhibit the new technology at the ees Innovation Hub from 7–9 May 2025, as part of The smarter E Europe in Munich. The Hub is ees Europe's new exhibition concept for young and innovative companies. Projects and products relating to energy storage will be presented in an attractive environment together with research institutes, start-ups and international companies. In addition, on all three days of the exhibition the ees Innovation Hub Stage offers a varied program on innovations from areas such as battery technologies, AI in battery research, recycling, as well as industry pitches. Community and networking events are a central component of the ees Innovation Hub in Hall B0, for example with the finalists and winners of The smarter E AWARD in the category Energy Storage. Also planned are a “4 o’clock beer” meetup, the “ees Islands Challenge” hackathon and an attractive meeting place for influencers, podcasters and TV teams.
