Fantasy Islands? Offshore wind's North Sea mega-hubs

IN DEPTH | Artificial islands in the middle of the North Sea could save the offshore wind industry up to €10bn a year, but will they ever be built? asks Anamaria Deduleasa in London

Man-made artificial islands are nothing new — Neolithic Celts and ancient Egyptians were building them up to 5,000 years ago — but no-one has ever tried to build one in a windswept sea 150km from the nearest shore. Until now.

Dutch-German grid operator TenneT and its Danish counterpart are planning to build a 6sq km island in the middle of the North Sea that will serve as an international offshore wind hub. It would connect to nearby wind farms and six countries’ national grids, and act as a cost-saving offshore wind construction and O&M base with shared transport and port facilities.

The flagship Power Link Island — which would include airstrips, worker accommodation, an artificial lake with a beach, and a large number of solar panels — is to be built on a huge North Sea sandbank called Dogger Bank, where water depths are only 20-40 metres.

“Building one or more artificial islands in the middle of the North Sea sounds like a science-fiction project, but it could actually be a very efficient and affordable way for the North Sea countries to meet the future demand for more renewable electricity,” says Torben Glar Nielsen, chief technology officer of

The island would connect to offshore wind farms around the North Sea using relatively cheap alternating-current (AC) cables, with the electricity stepped up to high-voltage direct-current (HVDC) by up to 15 on-site 2GW converter stations — eliminating the need for expensive converter platforms and substations at sea. The energy would then be sent along HVDC transmission lines to up to 100 million people in the UK, Germany, the Netherlands, Belgium, Norway and Denmark, with these so-called Wind Connector cables also serving as interconnectors between countries, allowing energy to be traded across the North Sea.

“In effect, the island will act as the spider in a North Sea web of offshore wind farms and international connections,” explains TenneT in a statement.

North Sea Wind Power Hub gets sign-off

Read more

This Wind Connector part of the project would allow offshore wind farms to sell their energy to whichever market offered the highest price, thus increasing revenues in the looming post-subsidy environment. The interconnector aspect will also ensure that clean power is flowed to where it is most needed, allowing the proportion of variable renewable energy in Europe to be increased.

This will also allow a significant reduction in the cost of exporting offshore wind power — export-cable utilisation from a Wind Connector would be close to 100%, as opposed to the average 40% from existing offshore wind farms (due to the variable nature of wind power and turbine downtime).

TenneT estimates that the cost of an island will be about €1.5bn ($1.6bn), with the North Sea Wind Power Hub project — which could consist of several such islands — saving the offshore wind industry €5bn-10bn per year.

The transmission system operators (TSOs) are to spend the next three years preparing the groundwork for the project — which would be built after 2030 — before entering the “realisation stage”.

“We are now in the research stage, looking at what benefits potential partners would have, and in parallel, we’re talking to NGOs [non-governmental organisations] to see what the implications of building such a development would be,” says TenneT business development manager Rob van der Hage. “Detailed technical development will become important in the next few years, before we start work on the initial stage. Right now, we are focusing on convincing the world this is a good idea.”

Peder Østermark Andreasen, chief executive of, is already convinced. “It is important to constantly focus on further reduction in prices of grid connections and interconnections,” he says. “We need innovative and large-scale projects so that offshore wind can play an even bigger part in our future energy supply.”

"We need innovative and large-scale projects so that offshore wind can play an even bigger part in our future energy supply"

Maros Sefcovic, the vice-president for energy union at the European Commission, is also fully behind the scheme.

“The North Sea Power Hub and the wind farms around it could add another 100GW to the current potential,” he enthused in March, adding that even 230GW was possible.

As it works to make the project a reality, the two TSOs will have to enter into talks with the EU and its soon-to-be 27 member states (as well as the UK) — to agree on co-operation terms. At the moment, there is no precedent for such an international project — or the territorial status it would have — and it raises all kinds of questions regarding legal issues, regulations, targets and financing.

They also have to convince other TSOs to join the project. “The ultimate goal is to build a solid coalition of companies that will make the European energy transition feasible and affordable,” says TenneT chief executive Mel Kroon. “The success of the energy transition depends largely on the extent to which we mount a co-ordinated joint effort in Europe.

“Co-operation between national governments, regulators, the offshore wind industry, national grid administration and nature and environmental organisations is a precondition for achieving Europe’s environment targets.

“It will be very important for the six 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.”

Van der Hage says that TenneT and are working on expanding the group of participating countries beyond Germany, Denmark and the Netherlands.

“Considering the location [of Dogger Bank], we would welcome the co-operation of the UK on this, and we even chose to ignore Brexit in this respect, since such a project would have a lot of potential for the UK as well and the other North Sea countries.”

He does add, however, that if the UK does not want to be involved, “there is a lot of potential in the Dutch and German North Sea areas”. While most of Dogger Bank, including the shallowest parts, is in UK waters, the sandbank also stretches into Dutch, German and Danish territory.

WindEurope chief executive Giles Dickson says that for the North Sea Wind Power Hub to be financially viable, the island would require at least 70GW of offshore wind capacity connected to it, requiring major engagement and investment by the wind industry.

Offshore wind 'could supply 25% of EU needs'

Read more

“The TenneT Island is a very long-term project, probably beyond 2030,” he says. “In the meantime, we need to focus on securing the right volumes and grid connections between now and 2030,” referring to the fact that only the UK, Germany and the Netherlands have so far signalled their ambitions for offshore wind after 2020.

“Despite having delivered cost reductions ahead of its self-imposed schedule, the industry needs at least 4GW per year after 2020 to continue reducing costs,” adds Dickson.

Major industry players acknowledge that the island would bring benefits, but they also warn that its realisation will depend on the close co-operation of the energy industry.

“It’s very encouraging that the TSOs see the great potential for offshore wind in the North Sea, and that they see the need to work across countries and radically ramp up the transmission infrastructure to integrate offshore wind power,” says Ulrik Stridbæk, spokesman for Denmark’s Dong Energy, the world’s largest offshore wind developer.

According to Stridbæk, the proposed hub should be included together with other possible solutions in a “thorough technical and commercial feasibility analysis”.

“In our view, it is important that we now look at transmission with fresh eyes,” he says.

“We have seen tremendous cost reductions and innovation in offshore wind power, which has been driven by the developers and the supply chain.

“We must make sure that we now see the same development on the transmission part.” 

Read Next

The risks of zero-subsidy offshore wind

IN DEPTH | Dong and EnBW say that the 1.38GW of subsidy-free offshore wind they recently won at tender will be profitable — but only if certain predictions come true

06 Jun 08:58 GMT