This week construction work started on Princess Elisabeth Island, an artificial energy island off the Flemish coast, 45 kilometres out in the North Sea. The first of a total of 23 caissons were sunk at their final location. Caissons are watertight structures used as a foundation element, particularly in construction projects involving water or underground work. This is a technically complex operation involving around 150 people.
Each caisson weighs 22,000 tonnes, is 58 metres long, 28 metres wide and between 23 and 32 metres high. The concrete blocks are transported from the Dutch port of Flushing, where they are being built, by four powerful tugs. This happens via the Western Scheldt and the North Sea over a distance of almost 100 kilometres.
Lowering the caissons is done with the utmost precision, also taking into account tides and weather conditions. To lower the blocks to the seabed in a controlled and stable way, they will be filled with water. The caissons will form the contours of the future island.
Ready for summer storms
The next construction phase consists of dumping stones around the sunken caissons to protect them against any summer storms, filling the caissons with sand, and preparations for placing the next caissons.
The gap between the caissons will be sealed to prevent sand from escaping later. The high-voltage infrastructure, which will be connected to the new offshore wind farms, will then be placed on top of the construction.
In the coming months, the eastern side of the island will be finished first, after which work will start on the southern side started. The speed at which this will be done depends entirely on weather conditions.
Princess Elisabeth Island is a “crucial link”
The works are being commissioned by high-voltage grid operator Elia and are being carried out by TM Edison, a consortium of the Belgian companies DEME and Jan De Nul. The works progress in close cooperation with the MRCC (Maritime Rescue and Coordination Centre in Ostend), the Joint Nautical Authority and the North Sea Port.
'Emergency procedures, maritime evacuation plans and strict communication protocols have been drawn up in accordance with the highest safety standards. All those involved have been trained accordingly,' Elia insists.
The system operator says the island is 'a crucial link in the access to future offshore wind farms in the Belgian North Sea (...) and both technologically and economically the most efficient way significantly to expand Belgium's offshore electricity production and reduce dependence on fossil fuels.'