Elestor, Windpark Zeewolde partner on 10-40-hour hydrogen-iron flow battery LDES project in Netherlands

The company says its technology can deliver storage durations of 8 to 150 hours. Image: Elestor.

Dutch long-duration energy storage (LDES) developer Elestor has partnered with Windpark Zeewolde to deploy a 20MW/200-800MWh hydrogen-iron flow battery storage system at what is described as Europe’s largest onshore wind farm.

Windpark Zeewolde is a 322MW wind farm located in the Flevoland province of the Netherlands, comprising 222 turbines developed by a cooperative of local farmers and landowners.

Despite generating substantial renewable energy, the plant faces a common constraint across the Netherlands. Grid congestion prevents it from exporting all its available generation during peak periods.

The partnership with Elestor is structured as a phased deployment, with the system scaling from an initial configuration up to 800MWh as the project demonstrates its performance and commercial case.

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Elestor’s hydrogen-iron flow battery technology stores energy in liquid electrolytes held in external tanks, with power and energy components decoupled to allow independent scaling.

That architecture makes it particularly suited to long-duration applications. Energy capacity can be increased simply by adding more liquid electrolyte, an extremely low-cost component, without duplicating the power infrastructure.

The company says its technology can deliver storage durations of 8 to 150 hours, well beyond what 4-hour lithium-ion systems can achieve, and the Windpark Zeewolde deployment will operate in the 10 to 40-hour range depending on dispatch requirements.

The partnership follows Elestor’s €30 million (US$34 million) Series A funding round, led by Equinor Ventures with participation from Vopak Ventures, Invest-NL, Somerset Capital Partners, EIT InnoEnergy and Enfuro Ventures.

Elestor has also received €22 million through the Dutch National Growth Fund’s SLDBatt (Sustainable Long Duration Battery) project consortium, which is focused on scaling long-duration electricity storage technology toward commercial deployment.

Flow batteries in a market dominated by lithium-ion

The Elestor-Windpark Zeewolde partnership sits within a European long-duration storage sector where flow battery developers have struggled to scale commercially despite strong technical arguments for the technology’s role in the energy transition.

As Energy-Storage.news has reported on the mixed fortunes of the flow battery industry, the sector holds genuine potential for long-duration applications but has faced persistent challenges around cost, manufacturing scale and competition from falling lithium-ion prices.

Several flow battery developers have entered administration or restructured in recent years, while others, including Elestor, Invinity and Sumitomo Electric, continue to advance commercial pipelines.

The Netherlands presents a compelling market for long-duration storage given the severity of its grid congestion problem.

The country has seen a rapid expansion of wind and solar capacity, but transmission network expansion has not kept pace, creating bottlenecks that prevent renewable energy generators from exporting available output.

TenneT, the Dutch transmission system operator (TSO), has been actively seeking commercial storage solutions to help manage that congestion. The organisation signed its first controllable congestion mitigator BESS contract earlier this year.

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