Flow battery Elestor offers large-scale storage of electricity

As low costs for electricity storage as possible. That is what drives Elestor. The company developed a flow battery based on hydrogen bromide. When you think of a battery, don't think of something that fits in your pocket, but think of a large factory, a large-scale, stationary battery that can store the electricity surplus from wind farms and solar farms for a long time. For this idea, Elestor was nominated for the Offshore Wind Innovators Award.

The management of Elestor, from left to right Wiebrand Kout, Hylke van Bennekom and Guido Dalessi.

The small household lithium batteries have a high energy density but are economically unsuitable for storing large amounts of electricity; a substance such as lithium is far too scarce and too expensive for large-scale application.

Elestor founder Wiebrand Kout foresaw that large-scale storage of electrical energy would be necessary to balance the unpredictable amounts of wind and solar energy with the energy demand. In 2014, he started developing a scalable flow battery that charges with the surplus of wind or solar energy and supplies power when the demand for electricity peaks.

From sea water

The flow battery consists of two parts, separated by a membrane that selectively allows ions to pass through. Elestor batteries are filled with hydrogen bromide. By adding electricity, the hydrogen bromide is split, and hydrogen ions (protons) are released, which then cross the membrane and form hydrogen. That hydrogen is stored in a separate tank, which is necessary for discharging. When the battery discharges, hydrogen bromide is produced again, and the electricity is released.

“This battery is all about the cost of energy storage. Hydrogen bromide is twenty times cheaper per MWh of storage than, for example, vanadium, which is currently widely used. Why? Bromine and hydrogen are abundantly available and resource extraction is not limited to a few countries. It is simply found in seawater and is a by-product of sea salt extraction,” says Guido Dalessi, CEO of Elestor.

“A positive by-product is that we can integrate the batteries with a hydrogen pipeline. We then use it as a virtual tank: the battery adds hydrogen during charging and extracts the same amount of hydrogen again during discharge. Then we no longer need the hydrogen tanks. That further reduces storage costs.”

Next step

“With the help of various investment rounds, we have realized a functioning battery with the size of half a sea container,” says Dalessi. “We will take the next step in 2023, thanks to a strategic partnership with Vopak, with who we will scale up the technology. The ultimate goal is to build a 250 MWh battery in Vlissingen in just a few steps. Vopak - now an investor in Elestor - understands the storage of large quantities of chemicals and works worldwide. We can create upscaling with them by equipping the batteries with very large tanks. In this way we can realize large-scale long-term storage of electricity.

At the moment we are mainly looking for customers who can help to increase our production capacity, which will eventually make the batteries very cheap. One of our shareholders is the Norwegian energy company Equinor, which operates large wind farms, among other things. Large-scale electricity storage is essential for such projects. In the long term I can also envision a smaller format, at individual windmills, such as at farms, or next to a distribution centre with a roof full of solar cells.”


You can no longer call Elestor a startup, with 38 employees of twelve nationalities now and an intended growth to a hundred employees by the end of 2024. Dalessi: “It is quite puzzling in the current labour market, but we notice that we have the wind in our back because we have a making a climate-friendly product and contributing to a cleaner energy supply. We also see people from the fossil sector looking for a job with more meaning. We believe that our batteries will completely replace fossil power stations. Something like that appeals.”

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