Heerhugowaard | S4 energy

S4 Heerhugowaard
Reliable by design

Screenshot 2026 01 05 at 19 38 51

In Development

Ready-To-Build

Under Construction

Site In Operation

About S4 Heerhugowaard

S4 Heerhugowaard was originally developed as a hybrid energy storage facility combining advanced flywheel technology with a 9 MW / 9 MWh (1-hour) battery system to deliver fast frequency regulation and grid-balancing services. In 2025, the site was upgraded and fully rebuilt into a 10 MW / 47 MWh (4-hour) battery system, future-proofing the asset and enabling a shift from the FCR market to aFRR, providing longer-duration, more effective grid support.

Project Details

Capacity 10MW / 47MWh
Duration 4 hrs
COD 2025 (4hr system)
Location Heerhugowaard, NL
BESS OEM Tesla
Grid operator Liander

S4 Heerhugowaard 2

Project Highlights

  • Evolved from hybrid storage to a 4-hour battery system supporting grid balancing and aFRR
  • 10 MW / 47 MWh BESS delivering long-duration grid balancing and aFRR services
  • Upgraded to future-proof the site as renewable generation continues to grow
  • Developed in close cooperation with local authorities in North Holland

Impact

It is estimated to avoid up to 8,000–10,000 tonnes of CO₂ emissions annually, equivalent to:

  • Approximately 4,500–5,500 cars taken off the road
  • Clean power flexibility comparable to 5,000–6,500 homes each year
  • Avoiding the emissions of roughly 2,400–3,000 flights
  • Equivalent to the annual CO₂ absorption of 400,000–500,000 trees
S4 Heerhugowaard 1

Frequently Asked Questions

Renewable energy from wind and solar is not always produced when it is needed. This creates congestion on the electricity grid and wasted potential. By storing energy when supply is high and releasing it when demand is high, battery storage keeps the grid stable and ensures renewable power is always available.

Commissioned in 2022, the S4 Heerhugowaard BESS plays a key role in supporting the energy transition in the Netherlands by providing fast and reliable grid-balancing capacity as renewable generation continues to grow. By combining rapid-response capability with longer-duration energy delivery, the project helps stabilise the electricity system, enabling higher penetration of wind and solar power. This grid stability is essential to reducing reliance on fossil-based generation and directly supports the Netherlands’ ambition to reduce CO₂ emissions by 55% by 2030 as part of its pathway to a carbon-neutral future.

Strategically, S4 Heerhugowaard reflects S4 Energy’s forward-looking approach to asset management. Rather than remaining static, the site has been actively future-proofed to evolve in line with rising power demand and changing system needs. This ensures the asset continues to deliver long-term value and remains relevant as the Dutch energy system becomes increasingly renewable and flexibility-driven.

Technically, the project stands out through its hybrid origins and evolution. The site combines flywheel technology with a 10 MW / 40 MWh battery system, enabling both ultra-fast response and sustained grid support. This configuration demonstrates how advanced storage technologies can be integrated and adapted over time to meet increasingly complex grid requirements.

The S4 Heerhugowaard BESS is designed and operated in full compliance with the highest Dutch and international safety standards. The installation adheres to PGS 37-1 guidelines for permitting and construction, ensuring safe design, installation, and operation of all electrical systems. All battery systems are IEC- and UL-certified, including UL 9540A–tested technology to provide proven fire and thermal safety performance.

The project is supported by a comprehensive fire safety and emergency response plan, reviewed and approved by the relevant fire brigade and environmental authorities. S4 also meets all Dutch legal requirements for BHV (bedrijfshulpverlening), with trained and annually recertified personnel on site. In addition, all technicians are VCA-accredited, and selected staff hold NEN 3840 certification for the safe operation and management of electrical installations.

Cooperation for the S4 Heerhugowaard BESS was organised through close coordination with the municipality of Dijk en Waard and the Province of North Holland, ensuring alignment with regional sustainability objectives and spatial planning policies.

The project team engaged transparently with landowners and nearby residents, providing clear information on the project’s purpose, design, and safety measures. This collaborative approach supports local acceptance while contributing to regional climate goals and reinforcing Heerhugowaard’s role in the Dutch energy transition.

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