Milestone: Dutch wave energy device trialed off Scheveningen coast

In early March 2025, Dutch company Slow Mill Sustainable Power reached another major milestone by deploying and testing its wave energy converter in the North Sea, just off the coast of Scheveningen, The Hague. This marks one of the few wave energy trials conducted in Dutch waters, and is a significant step toward adding wave power to the Netherlands’ offshore energy mix. The goal of this trial was to validate installation procedures, test operational systems, and collect performance data in real sea conditions.

Technology Overview

The Slow Mill is a heave-and-surge wave energy converter (WEC) designed to harness both vertical and horizontal wave movements. Its floating structure, equipped with blades extending 3–4 meters below the surface, follows the orbital path of waves, allowing it to capture energy efficiently even in "milder" wave climates such as the North Sea. The device's design ensures minimal phase lag with incoming waves, a concept referred to as "hyper resonance," optimizing energy extraction also in irregular waves. The prototype, rated at 40 kilowatts measures 8 meters in length, 12,5 meters in depth, and features a 2.5-meter diameter floater. Plans are underway to scale up to a 400 kW unit, aiming to provide energy for around 100 households for the island of Texel, followed by array deployments.

Benefits

Beyond energy generation, the Slow Mill offers additional benefits:

• Coastal protection: by dampening wave energy, it reduces the need for sand replenishment projects.

• Environmental enhancement: the anchor structure promotes marine life by serving as an artificial reef, increasing biodiversity.

• Synergy with wind farms: its integration into existing offshore wind farms is feasible, utilizing shared infrastructure like subsea cables.

Funding and next steps

The project has been supported by InnovationQuarter, as part of the Province of South Holland’s Energy and Climate Program and the Waddenfonds.

With growing demand for renewable energy in coastal and island communities, such as the Wadden Islands, as well as in international markets, the next steps include bringing this technology to new seas and communities. A key future opportunity lies in potential integration with offshore wind farms, which is seen as a promising and high-impact application that could significantly contribute to the Netherlands’ offshore energy mix by 2032.

Stay connected

For more information and to follow our progress, please visit Slow Mill and follow them on LinkedIn.