Seventeen of the total of 23 caissons have been installed at the Princess Elisabeth Island site, 45 kilometres off the Belgian coast, where TM Edison, a consortium of DEME and Jan De Nul, is building the first artificial energy island in the world.
Developed by Belgium grid operator Elia Group, Princess Elisabeth Island will serve as a key connection point for transporting electricity generated by future offshore wind farms in the Princess Elisabeth Zone to the mainland.
The installation of the caissons, massive concrete structures that will form the outer walls of the island, started in April 2025, with the first campaign completed in October 2025. The work resumed this spring.
At the beginning of this year, Jan De Nul said it had constructed the remaining concrete structures for the energy island.
Each of the caissons weighs approximately 22,000 tonnes and measures 58 metres in length, 28 metres in width, and between 23 metres and 32 metres in height, depending on the presence of a storm wall.
The Princess Elisabeth Zone comprises three sites totalling up to 3.5 GW in offshore wind capacity that will connect to the island’s infrastructure.
The tender process for the first of three lots, planned to house a 700 MW offshore wind farm, was launched in November 2024, with the winner expected to be announced in December 2025.
However, in 2025, the Belgian Council of Ministers decided to postpone the tender for the Princess Elisabeth Zone I site and said the procurement would be opened in 2026.