Challenges and innovations for the installation of the Princess Elisabeth Island, the world’s first offshore energy island
Type:
Presented during:
CEDA Dredging Days 2026
Authors:
K. Van Doorslaer and R. Duyver
Abstract
The Belgian part of the North Sea will become home to the world's first offshore energy island, an island of 520m long by 230m wide where array cables from Belgium's 2nd offshore wind zone will arrive. Interconnectivity with other European countries is made possible too. The island consists of 23 caissons, each 57 m long, 28 m wide, ca 21.5 m high with wave walls up to 9.5m. Each caisson consist of 55 cells of 5m by 5m. The detailed design and caisson construction are completed, and the offshore installation has passed the halfway milestone. Upon completed caisson installation, the island will be reclaimed, and its top surface will be finished. Offshore cables will be connected to the island in the years after handover. The presentation will show the project progress with a focus on the challenges met and innovations used in the offshore installation and hydraulic filling of the caissons. Just before installation, an offshore survey and a high spot assessment are performed, to evaluate if the reinforcement capacity of the base slab can deal with the unevenness of the rock mound. The caissons are then waterfilled until touchdown, within very accurate installation tolerances, and further filled until overflow. Waterfilling is done via pumps that hang from the caisson outer walls. A Trailer Suction Hopper Dredger then connects via a bow coupling to the water- and sandfilling pipes and fills the caisson cells with sand until overflow. The sandfilled caissons with a completed toe rock protection are stable against winter storms. After all caissons are installed and rockworks are completed, the island reclamation and compaction will be performed, further increasing the caisson's stability. The sand used for caisson- and island fill comes from the project area, sand that would erode otherwise due to the island presence.