Elia Transmission Belgium and the TM Edison consortium have installed the 23rd and final caisson for the Princess Elisabeth Energy Island, 45 kilometres off the Belgian coast in the North Sea, completing the foundation works for the project.
The 23 caissons form the protective outer perimeter of the artificial island. Each measures 58 metres long and 28 metres wide, stands between 23 and 32 metres high depending on whether it carries a storm wall, and weighs roughly 22,000 tonnes. They were built in Vlissingen in the Netherlands, with around 300 people working on the site each day and about three months required per unit, before being towed out and set down offshore.
“The completion of the foundation construction work represents a major step for us in the expansion of Belgium’s offshore energy infrastructure, which plays a key role in the energy transition and boosting our energy independence,” said Frédéric Dunon, CEO of Elia Transmission Belgium.
Work now moves to rainbowing — feeding sand into the caisson structure to build up the island itself. Cable connections to shore are scheduled for 2027 and 2028, electrical infrastructure installation for 2029, and final completion for 2031. The island is designed to connect Belgium’s second offshore wind zone and leaves open the option of a future interconnector with the United Kingdom.
Delivering the foundations within the agreed window allows Elia to claim €99 million in European Union support earmarked for this phase. The caissons were also designed with a nature-inclusive brief: as part of the Reefcovery project, young oysters were raised on rocks installed around the island in late July, intended both as erosion protection and as the basis for a new oyster reef.
TM Edison is a consortium of DEME and Jan De Nul. “Transporting and installing 23 concrete caissons, each weighing some 22,000 tonnes, demanded meticulous preparation and execution,” said Gert De Smet, Princess Elisabeth Island Project Director at DEME. For Baltic Sea planners weighing hub-and-island concepts of their own, the Belgian project remains the closest thing to a live reference case.
