Forty-five kilometres off the Belgian coast, in the middle of the North Sea, humans are creating something that did not naturally exist in the water. It is the world’s first artificial energy island the size of eight football fields, being built with 23 giant concrete caissons, each weighing approximately 22,000 tons. While one might assume that the island would house humans or grow a wildlife sanctuary, its purpose is none of these. It is being built to collect all the electricity generated by future Belgian offshore wind farms and send it to the mainland via submarine cables.The project known as Princess Isabel Island is being promoted by the Belgian electricity system operator Elia. It is being built by the TM Edison consortium, formed by the Belgian engineering firms DEME and Jan De Nul. At the end of January 2026, those in charge announced a key milestone: the last caisson had been manufactured and was afloat. And that’s when the decisive phase begins.
A power source
In total, the operation spans two years, with pauses during the winter storm season.
Each box measures approximately 58 metres long, 28 metres wide and between 23 and 32 metres high, depending on the configuration of the storm walls. They were manufactured in the port of Vlissingen (Netherlands), on a production line with five stations that allowed work on several units simultaneously. The complete process for a single block takes around 85 days.DEME confirmed in January 2026 that the final caisson was completed and launched, marking the end of the manufacturing phase. Now, the pieces are transferred to the Scaldia terminal for final finishing before their final installation in the sea.The blocks will not be simply launched into the water and sunk. They will be towed partially submerged to the site, where dredges and ships have previously prepared a bedrock foundation. Once in position, they will be filled with sand so they can sink and rest on that base. The first immersion campaign began in April 2025 with two caissons. It ended in October and will resume this spring of 2026, weather permitting. In total, the operation spans two years, with pauses during the winter storm season. The complete installation cycle—from departure from the port to placement and fixation at the final destination—takes about 24 hours.The island is vital for the European electricity system. It is not an end in itself but a distribution hub. Its infrastructure will combine high-voltage alternating current (HVAC) and high-voltage direct current (HVDC), a very uncommon mix at sea and central to the project’s classification as the world’s first ‘energy island’.In practice, it will consolidate the submarine cables for the new wind farms that will occupy the so-called Princess Elizabeth Zone, a 285-square-kilometre strip of land intended to produce up to 3.5 GW of offshore wind energy. This electricity will then be transmitted to land via high-capacity cables.Furthermore, it is planned to connect with future international interconnectors (Nautilus with the United Kingdom and TritonLink with Denmark), which will allow the exchange of electricity between national networks according to demand and renewable production available at any given time.
Nature inclusive
The design is not limited to just being concrete in the middle of the sea. Elia and her partners worked with marine conservation experts under an approach called “nature-inclusive design” something like design integrated with nature. The exterior walls incorporate protrusions for the roosting and breeding of the kittiwake, a species classified as threatened in the North Sea. There are also submerged structures for marine organisms and specific solutions for the European flat oyster. The NID4BirdLIFE program, co-funded by the European Union’s LIFE program, will monitor the nests’ development for six and a half years using cameras installed in the walls themselves.The economic figures reflect the scale of the effort. In October 2024, the European Investment Bank approved €650 million in financing for Elia Transmission Belgium for the first phase of the project, with a total estimated cost of €1.105 billion. But, the project has been hit by a dramatic increase in costs, which have risen from an original estimate of €650m to €7bn. This surge is primarily due to increases in the cost of electrical equipment and has raised concerns about the project’s viability.According to available data, the bulk of the civil engineering work should be completed by mid-2026. The electrical infrastructure itself will be installed between 2026 and 2030. The island should become operational around 2030, in parallel with the new wind farms and the onshore Ventilus and Boucle du Hainaut projects, which are responsible for delivering electricity to the end consumer.
