TenneT Presents ‘Hub and Spoke’ Offshore Wind Concept (VIDEO)

TenneT has presented a ‘hub and spoke’ concept to set up a large European offshore electricity system that incorporates building of an island in the middle of the North Sea.

Image: TenneT

Numerous wind farms can be connected to the artificial island – a total capacity of over 30 GW can be connected on an island of roughly 6 km² – from where the generated wind electricity will be distributed and transmitted over direct current cables to the North Sea countries, i.e. the Netherlands, the United Kingdom, Belgium, Norway, Germany and Denmark.  The same direct current cables will be serving as interconnections between the energy markets of the aforementioned countries, so besides distributing electricity generated by wind they will also be international electricity highways for international power trade – the Wind Connector, TenneT explained.

TenneT said it will enter into talks with the EU and the Member States to see whether the required European cooperation can be set up. Factors that play an important role include legislation, regulation, targets and financing.

The offshore grid operator will further make a start on studying IJmuiden Ver in terms of engineering, interconnection, conversion, shore feed-in and integration with existing infrastructure. Also, there will be an examination together with UK stakeholders of possibilities for connecting IJmuiden Ver to a UK wind energy area, possibly East Anglia.

Mel Kroon, TenneT CEO, said: “It will be very important for the six European North Sea countries to be willing, in due course, to make their targets independent of national borders, which means agreeing that the electrons generated offshore must not necessarily be transmitted to their own country.” 

In TenneT’s vision, the creation of an island is not the starting point of this development, as before that stage is reached, it will first be necessary to utilise other possibilities. In sequence, these are onshore wind energy and near-shore wind energy. This development is necessary for the structural reduction of the costs of offshore wind energy, the company said.

The next, logical steps are:

  • The wind energy areas of Borssele, Hollandse Kust (zuid) and Hollandse Kust (noord) are already under development. According to planning, all will have entered service in 2023.
  • The offshore areas of IJmuiden Ver (5-6 GW) and possibly other wind energy areas already designated will be developed.
  • The possibility of international cooperation between IJmuiden Ver and a UK wind energy area, such as East Anglia, can be examined. This might also be feasible in combination with an interconnector to the United Kingdom and an island. This might be from 2025-2030.
  • The island could perhaps be built on the Dogger Bank, between 2030 and 2050.

An island at a location like the Dogger Bank offers numerous advantages, according to TenneT. The Dogger Bank is relatively shallow and is large with the space needed for large-scale wind energy. The shallower the water, the lower will be the cost of building the wind farms and the island. Another very important matter is that there is often a strong wind in that part of the North Sea. This produces a high yield of wind energy.

In short, an island in the middle of the North Sea offers everything necessary to make offshore wind energy a success, TenneT emphasised.

  • Large wind farms way out at sea will connect to an island. Far-shore will become near-shore, which means lower costs.
  • Direct current connections will double as interconnectors. The efficiency of these connections will increase from roughly 40% towards 100%.
  • People, parts and assembly factories can be placed on the island, thus optimising logistics in Europe.
  • The Dogger Bank has a lot of strong wind. This will optimise the yield.
  • The area is relatively shallow. The shallower the water, the lower will be the cost of building the wind farms and the island.
  • An island in an area with a lot of space will provide the scale necessary to reduce costs (through economies of scale).

In developing the Dogger Bank as a location for large scale offshore wind and an artificial island the impact on marine flora and fauna should be taken into account by the cooperating parties. TenneT has been in close contact with a number of environmental organizations. A first ‘quick-scan’ of the impact on flora and fauna on the Dogger Bank shows both opportunities as potential risks for animals and biodiversity.

Tjerk Wagenaar, director of leading Dutch environmental NGO Natuur & Milieu: “TenneT is a reliable state-owned partner that can help ensure a successful energy transition in the North Sea. They can do this cost-effectively, with a focus on sustainable and ecological values. It is precisely in large-scale projects of this kind that we have to take marine flora and fauna into consideration as much as possible.”

The present utilisation of a connection between a wind farm and the mainland is around 40%. This is because there is not always wind (or not always equally strong) and the wind turbines also have to undergo maintenance or repairs. In effect, the island will act as the spider in a North Sea web of offshore wind farms and international connections. This will increase the present efficient utilisation of a connection between the wind farm and the mainland from roughly 40% towards 100%, TenneT said.