Long-Duration Storage for Wind Power: Hydrogen-Iron Battery to Ease Dutch Grid Congestion
Zeewolde/Arnhem – Grid congestion is increasingly limiting the use of wind power in the Netherlands, as transmission capacity is often exhausted. Windpark Zeewolde, the wind farm operator, and storage developer Elestor plan to address this constraint with a long-duration storage system connected directly to the high-voltage substation.
Hydrogen-Iron Battery to Store Up to 40 Hours of Wind Power
Windpark Zeewolde and Elestor have agreed a partnership for the phased development of a hydrogen-iron flow battery at the Vogelweg site. The battery will be connected to the closed distribution network there, which also links the wind farm. The system is designed for 20 megawatts of power and, depending on configuration, 200 to 800 megawatt-hours of storage capacity, corresponding to a storage duration of 10 to 40 hours. The aim is to store wind power during periods of high generation and release it when demand rises or grid capacity becomes available again.
Development will proceed in phases: following a pre-commercial unit that Elestor says it plans to install next year, a commercial-scale system will follow. According to the project partners, the full 20-megawatt system is expected to be completed by 2031. Through the phased rollout, the partners aim to gain technical, operational and commercial experience and reduce risk.
Hydrogen-Iron Flow Technology: Power and Capacity Scaled Independently
In hydrogen-iron flow technology, the electrochemical reactions take place in a membrane stack of cells. Gaseous hydrogen circulates on one side of the membrane, an iron sulfate solution on the other. The iron ions exchange electrons with the hydrogen during charging and discharging, enabling the flow of electricity.
Because storage capacity depends solely on the volume of the two media held in external tanks, while power output is determined by the cell surface area, power and storage capacity can be sized independently of each other. According to Elestor, this allows storage duration to be scaled up to 150 hours in principle.
Arnhem-Based Storage Developer Elestor Moves Toward Large-Scale Deployment
With the project, Elestor aims to move its hydrogen-iron flow technology from pre-commercial testing into large-scale operation. The company closed a EUR 30 million funding round led by Equinor Ventures in 2022.
"For Elestor, this is an important milestone in scaling up our technology. The combination of large-scale wind production and long-duration storage shows how we can bring more flexibility, security of supply and renewable energy into the system," said Hylke van Bennekom, CEO of Elestor.
Windpark Zeewolde is owned by more than 200 farmers, residents and entrepreneurs from the region and, according to the company, is the largest onshore wind farm in the Netherlands with 320 megawatts of capacity. The storage system is intended to add a further function to the wind farm: going forward, electricity generated there can not only be fed into the grid but also stored temporarily.
"Windpark Zeewolde wants not only to generate renewable electricity but also to use it more intelligently. With this long-duration storage system, we are taking an important step toward the energy system of the future," said Maarten de Keijzer, managing director of Windpark Zeewolde.
Netherlands Pursues Action Program Against Grid Congestion
The Dutch government has launched its own action program, the Landelijk Actieprogramma Netcongestie (LAN), involving grid operators, municipalities and market participants. Part of the program is intended to help make better use of existing grid capacity before new lines and connections become available. Storage projects such as the one planned in Zeewolde make more flexible use, over time, of existing grid connections rather than waiting for new lines.
Source: IWR Online, 19 Aug 2026
