Right now, it’s merely a sandbank. A stretch of shallow water with high wind speeds in the heart of the North Sea. But if it’s up to TenneT, the Dutch-German Transmission System Operator, Dogger Bank will be transformed into an 6 km2 artificial island, a hub connecting all future wind farms in the North Sea by 2050. Its scale dwarfs current offshore sites.

Fulfilling the Paris Agreement obligations to limit global warming to 1,5 °C is a tremendous task. Equally, immense is the North Sea Wind Power Hub proposed by TenneT, the Dutch-German TSO. To create an artificial island the size of Rottumerplaat, 125 km east of East Yorkshire, requires a € 1,5 billion investment. In return this power hub will connect up to 100 GW of wind farms mid century, providing almost a fifth of all EU households with electricity.

But there’s a long, long way to go: in 2016, EU offshore wind farms have provided a mere 12,6 GW. Almost fifteen times as much – or 180 Gigawatts - at the North Sea will be necessary to meet the COP 21 goals mid-century.

International hub

Though the proposal of TenneT may be enormous by present-day standards, it offers huge advantages as well. Onshore, there’s not enough space to install such a vast amount of Gigawatts. The further offshore wind farms are from the mainland, the more expensive submarine power cables become, ranging up to 30 percent of its initial capital costs. An island in the heart of the North Sea reduces those costs substantially: cables will not only transfer energy to the countries connected to it, they also serve as interconnectors between markets of North Sea countries, enabling them to trade energy across national borders.

(At present all North Sea countries interconnect bilaterally, for instance with the COBRA cable between Denmark and the Netherlands, the BritNed cable between Kent (UK) and the Maasvlakte (NL) and the proposed Viking Link between Lincolnshire (UK) and southern Jutland, Denmark).

A homebase for offshore activities

Last but not least, combined with a harbour and an airport (or even an electric hyperloop between Schiphol Airport (NL), the Dogger Bank and UK’s Moray Firth ) such an artificial island will be a home base for operations and maintenance (O&M), jobs and equipment that are presently running out of ports to supply. O&Ms are essential for wind farms, comprising over 20% of LCOE (levellised costs of energy), rising the more they are further offshore.

One of the main features of TenneT’s proposal to interconnect is the use of HVDC (High Voltage Direct Current). As a rule of a thumb, the more miles you make, the cheaper DC becomes. At Kriegers Flak, a wind farm of 600 MW in the Baltic Sea between Danish Malmö and the German island of Rügen, such an approach is tested by DTU, the Technical University of Denmark. According to DTU, combining AC systems with DC connections, will increase reliability and efficiency as well as the flexibility of connecting all offshore wind turbines, crucial to balance intermittent resources.

Little sibling

So it’s not without reason that Port of Rotterdam and Gasunie have joined the consortium of TenneT and Energinet (the Danish TSO) last Autumn. Port of Rotterdam sees opportunities of such a power hub while Gasunie, the Dutch gas grid operator, is presently working on Power-to-Gas (P2G) pilots.

This may become the backbone of the North Sea Power Hub in the near future: P2G converts electricity to gas to store surplus energy for later use. It does so, either by electrolysis splitting water into hydrogen and oxygen or combining hydrogen with CO2 to form methane. After conversion, huge amounts of hydrogen can be stored seasonally in empty oil and gas fields and, when needed, transported to the mainland. The costs of transporting gas are considerably lower than electricity.

As a prelude to and a smaller version of the envisaged power hub at Dogger Bank, TenneT wants to create a power hub island of 13 GW at the border of the wind farms East Anglia (UK) and IJmuiden (NL) Construction is planned between 2025 and 2030.

International cooperation

Though the island at Dogger Bank is as ambitious as it is expensive, the plan has met a favourable response from energy companies and analysts alike. However, cooperation of energy companies is of utmost importance: though the consortium is wealthy and can provide for most of the investments, TenneT is not allowed to develop and build generation stations due to regulations. Therefore wind farm developers have to step in.

Ecological impact

Last but not least, such a huge wind project will undoubtedly raise questions about the preservation of marine flora and fauna, TenneT is fully aware of that. Dogger Bank is a Natura 2000 area. A first ecological quick scan shows limited change of biodiversity and biomass due to the power hub island. However, mitigation measures or limiting under water noise during construction are necessary to protect fish and sea mammals. Also more research is needed about the impacts on breeding grounds and foraging areas of migratory birds.

Image: Artist’s impression of the artificial island at Doggers bank. Courtesy: TenneT.