Belgian Energy Island in North Sea Starts Taking Shape (Video)
May 1, 2025
TM Edison, a consortium of Belgian marine construction companies DEME and Jan De Nul, has installed the first two of a total 23 caissons in the Belgian North Sea, marking the start of construction for the Princess Elisabeth Island, the ‘world’s first’ artificial energy island.
Caissons are concrete building blocks that form the outline of the future island. In a later phase, the interior will be filled with sand to build high-voltage infrastructure that will connect new offshore wind farms.
TM Edison is carrying out the work on behalf of grid operator Elia Transmission Belgium (Elia). In the coming decades, the energy island will become an essential part of Belgium’s electricity supply.
The transport and installation of the caissons at sea is a technically complex operation that began on April 21, 2025. Each caisson weighs approximately 22,000 tons and measures 58 meters in length, 28 meters in width, and between 23 and 32 meters in height, depending on the presence of a storm wall.
For the transport from the port of Vlissingen - where they are built - four powerful tugboats are used to tow each caisson via the Western Scheldt and the North Sea to the island site, covering a distance of approximately 53 nautical miles or 98 kilometers.
The complete installation cycle - from departure from the port to placement and fixation at the final destination - takes about 24 hours.
Once at its destination, the caisson is connected to pre-installed anchors and positioned above the foundation zone. The caisson is then filled with water, allowing it to descend to the seabed in a controlled and stable manner.
This is followed by the next construction phase which involves placing rock armor around the submerged caisson to protect it against potential summer storms, filling the caisson with sand, and preparing for the installation of the next caisson.
Finally, the opening between the caissons is sealed to prevent sand from escaping later when the interior surface is filled.
The Princess Elisabeth Island will be a crucial link in connecting future offshore wind farms in the Belgian North Sea. It is both technologically and economically the most efficient way to significantly expand Belgium’s offshore electricity production and reduce dependency on fossil fuels.
The project is therefore of major strategic importance and will be a key factor in Belgium’s electricity supply over the coming decades. In the longer term, the project also offers opportunities to integrate Belgium into a unified European electricity grid at sea. The Princess Elisabeth Island is one of the flagship projects of the Federal Development Plan for the Belgian high-voltage network, which was approved by the federal government in 2023.
The construction of the island and the implementation of the already signed alternating current (HVAC) contracts are continuing without interruption. Two of the three future offshore wind farms - or 60% of the new Princess Elisabeth Wind Zone – will thus be completed.
Due to the price increase for high-voltage direct current (HVDC) infrastructure, the decision on the final contracts for the Princess Elisabeth Island has been delayed.
Elia is carrying out the project within a legal framework but remains attentive to growing concerns over the rising costs of HVDC technology, the TSO said.
This delay is not without consequences but provides extra time to evaluate the current design against alternative concepts in a changing market context. Elia and the relevant federal authorities have been discussing this matter for some time, with the aim of supporting a well-founded political decision when it is made.
