In December, one of the most exciting electricity infrastructure projects in Europe took a step forward with an agreement for €99.7 million in financial support for the artificial Princess Elizabeth energy island, to be located 45 kilometres off the Belgian coast.
The funds, provided as part of the EU’s Recovery and Resilience Facility, will be used to build the five-hectare island’s foundations.
Planned by Belgium electricity system operator Elia, the island will eventually house electrical infrastructure to centralise the collection of offshore wind generation. It will also link offshore wind generation to the Belgian electricity grid and potentially to the UK and Danish grids via two proposed multi-purpose interconnectors (MPIs).
The project is thus the first major manifestation of the North Sea Super Grid, an emerging network of offshore wind farms and interconnectors, designed to facilitate the efficient and widespread use of the North Sea’s offshore wind resource across multiple European markets.
Building an artificial island is not the simplest of tasks, but for Belgium, which has only 65 km of coastline, it presents an innovative solution for the expansion of its offshore wind capacity.
The first step is a thorough investigation of the seabed to identify an area with suitable subsea geology. Environmental Impact Assessments (EIAs) are a must to assess the impact on marine life of both the new island’s existence and the construction process.
The next step is to build a retaining wall to protect the foundations of the future island from erosion as a result of waves and sea currents. This wall also acts as a breakwater to provide calm conditions for vessels engaged in the island’s construction. Without a breakwater, the island would be defenceless against the forces of the sea. Rock, steel pipe piling or concrete caissons filled with sand can be used for the containment wall.
The breakwater can later be strengthened by protective rock slopes to create multiple levels of defence against sea erosion. It may also be given a stone or concrete lining above sea level to protect from breaking waves, and concrete blocks can be deployed to break the force of waves before they impact the island.
Once the containment wall is in place, the next step is filling in. This involves the collection and deposition of sand within the containment wall to create the island’s foundation. Each metre of loose sand is subjected to ‘vibro-compression’ to hugely speed up the natural process of settling, which left to its own devices would take decades.
Any remaining gaps in the containment wall have to be sealed, so that the sea does not move or erode the sand within the containment area.
With the foundation in place, work can begin on the island’s harbour. This usually involves construction of an additional wall of metal sheets to create a dry area and then excavation of a pit so that harbour construction can take place. When complete, the metal screen wall and remaining sand are removed, allowing water to flood back into the harbour area, reconnecting it with the sea. The newly-constructed harbour allows the easy delivery of equipment and materials.
The island is now essentially complete and ready for construction of the infrastructure on its topside.
Princess Elizabeth Island is expected to take around seven to eight years to build. In 2023, the focus will be on tender procedures, EIAs, permitting, and applying for the grant of the domain concession for the energy island.
Building the island itself is expected to take about two and a half years. Then, from mid-2026 to 2030, topside construction and electrical infrastructure commissioning will take place.
The island is being built close to the protected Natura 2000 marine area and Elia, along with independent marine environmental experts, are adopting a ‘Nature Inclusive Design’, which aims to create new natural habitats around and on the island.
The island’s construction will be accompanied by a number of linked projects, not least the gigawatts of new offshore wind farms which will be directly connected to it. The island is expected to have 2.3 GW of offshore wind farm capacity connected and to facilitate up to 3.5 GW in total in Belgium’s second designated offshore wind farm area.
The project will also need a link from the island to the onshore grid and onshore grid re-enforcement. The former is known as the Ventilus project, which is planned for construction between 2024 and 2027, bringing offshore power onshore to a new electricity connection in West Flanders.
The latter comprises one of Elia’s most significant onshore infrastructure projects, La Boucle du Hainaut (Link in French), or Hainaut Loop.
This will reinforce electricity flows with the French grid and allow electricity generated offshore to penetrate further inland, bringing the benefits of clean offshore wind energy to more European consumers and businesses. Consisting of a high voltage line (380 kV) with transmission capacity of 6 GW, it will link the Avelgem and Courcelles substations and form part of a wider network of major European transmission lines.
The artificial island is expected to be linked to two MPIs, the Nautilus interconnector with the UK and Triton Link with Denmark.
Nautilus is a planned subsea interconnector with 1.4 GW of capacity. According to the developer, the UK’s National Grid Ventures (NGV), it will facilitate up to 2.8 GW of offshore wind, half sending power to the UK and the other half exporting to Belgium. Spare capacity on the line, when wind generation is low, will be used for additional electricity trade between the UK and Belgian markets.
Proposals for the link to make landfall in the UK county of Suffolk have generated significant concern over its environmental impact on the Suffolk coast. NGV says it is considering moving the landing point to the UK’s Isle of Grain further south. Given its early stage development and need for permitting, the Nautilus project is not currently expected to be operational until 2028.
Triton Link will provide a link to Danish offshore wind farms and will be connected to Denmark’s own proposed energy islands. It will be about 600 km long and has been proposed by Elia and Danish system operator Energinet. Construction of the MPI is expected to take four years and should be complete around 2030.
Denmark is planning two energy islands, one using the existing island of Bornholm and the other an artificial island.
3 GW of offshore wind capacity is planned for Bornholm and a further 3 GW, eventually rising to 10 GW, for the artificial island. The project plan for the new island is still under development, with a combination of reclaimed land and floating structures being assessed. Completion is currently targetted for 2033.