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In Heerhugowaard, S4 Energy has started a pilot with a hybrid energy storage system to achieve a constant flow of energy at Wind Farm Luna. The innovative system consists of a combination of batteries and KINEXT flywheels. In addition to improved energy flow from the wind farm, the system ensures stability of the grid frequency at 50 Hz, even when the wind is momentarily not blowing. This allows the wind farm, which is managed by Eneco, to supply renewable energy to the grid even more efficiently.

With this innovative pilot, S4 Energy and Eneco want to bet on an energy storage system that can improve net returns from wind farms, by improving the outgoing profile of the wind turbines. At the same time, it reduces imbalance in supply and demand for renewable energy and potentially prevents curtailment.

Longer service life

The combination of a battery with the KINEXT flywheels allows immediate response to variations in mains frequency with sufficient power. In addition, the KINEXT flywheels also ensure longer battery life. The flywheels can supply or withdraw large power from the grid in a short period of time, greatly reducing the load on the batteries and keeping the charge status of the batteries around 50%. This increases the lifetime of the battery system.

Funding the pilot

This innovative pilot will receive a DEI grant from RVO. In addition, financing is made possible by the Participatiefonds Duurzame Economie Noord-Holland, which has been involved in the development of S4 Energy’s system as an impact investor since 2028.

Commercial Director of S4 Energy, Dominique Becker Hoff: “In Heerhugowaard we are now installing for the first time an integral energy storage system directly connected to a wind farm. By combining the experience of our other energy storage systems with this project, we are all set to accelerate our business and expand our services.”

Lucien Wiegers, commercial director Eneco Energy Trade, said, “For the integration of renewable generation assets in our energy systems, it is important that we can respond well to the differences in energy supply and demand. S4 Energy’s system offers the combination of storage and direct balancing of energy flow from a wind farm. This is another great step forward.”

Joost de Waard, Investment Manager PDENH: “Because we believe this type of system is necessary for large-scale deployment of renewable energy sources, we have been on board with S4 Energy as a financier since 2018. Nice to see, that the installation in Heerhugowaard is now “live”!”

About S4 Energy

S4 Energy ( optimizes energy networks with turn-key, scalable and flexible energy storage solutions that incorporate in-house developed hardware as well as software. In addition to its broad energy storage knowledge, S4 Energy has also developed a unique proprietary storage technology, KINEXT. In Heerhugowaard, S4 Energy completed its second hybrid storage system, a 10 MW battery with a 3 MW KINEXT flywheel system. Together with its system in Almelo, S4 Energy is now able to offer 18 MW of system services in the market.

About Eneco

Eneco consists of a group of companies active internationally in renewable energy and innovation. Together with our customers, partners and nearly 2,800 employees, we are working on our mission: sustainable energy for everyone. We invest in wind farms, biomass plants, heat and solar farms to increase the supply of renewable energy. And we develop innovative products and services so that our customers can control how energy should be generated, stored, used or shared.


PDENH was established by the province of North Holland with the aim of stimulating the sustainable economy in North Holland. The fund invests in companies and projects focused on energy transition, circular economy and sustainable mobility. The fund has a size of €85 million and has invested in more than 30 companies and initiatives since its inception. PDENH is managed by KplusV and Startgreen Capital.


Contact S4 Energy

Karin Husmann

[email protected]



Contact Eneco:

Rianne de Voogt

[email protected]

06 1141 8016

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