Transmission system operators Tennet and Energinet, gas infrastructure company Gasunie and the Port of Rotterdam have carried out a project assessment for their North Sea Wind Power Hub.
They hope to integrate 180GW of offshore wind in the North Sea by 2045 — a figure they believe necessary to help meet the goals of the Paris Climate Agreement. There is currently just under 13GW installed in the North Sea.
Under the plans — first unveiled in 2016 — wind farms would be connected via islands to shore using electricity transmission cables.
The project partners initially envisaged one large hub connecting North Sea wind farms, but are now targetting several smaller hubs.
These can "better respond to local circumstances" than one centralised hub, a Tennet spokesman told Windpower Monthly.
The first of several energy islands could be completed in the early 2030s.
An initial roll-out of a hub capable of connecting between 10GW and 15GW of offshore wind capacity would be "the next logical step" towards an eventual expansion of up to 180GW by 2045.
The partners are examining three types of hub: sand-filled islands for larger connection capabilities, air- and watertight caissons, and steel jacket- or gravity-based platforms similar to those already used for converter stations.
Electricity generated at wind farms connected to these hubs would initially be carried to land via electric cables, and then converted to gas onshore to add flexibility to the energy system.
The project developers added that large-scale power-to-gas conversion would not be technically feasible at sea in the early 2030s, and so this would need to take place on land.
However, as costs continue to fall and the technology matures, power-to-gas conversion could take place offshore as well as onshore, the Tennet spokesman said.
It is "probably possible" to construct the first energy island while adhering to the existing legislative framework and within the current market design in Europe, the project partners stated in their assessment.
International cooperation will be necessary to facilitate cross-border interconnectors and the standardisation of direct-current voltage levels, as well as support long-term forward planning.
A coordinated approach to offshore wind development could be cheaper than continuing with the current national approach, the consortium added.
They believe a 30% cost reduction over the life-cycle of the connected wind farms could be made possible, compared to 180GW of non-internationally coordinated offshore wind development.
The consortium has begun discussions with governments, non-governmental organisations (NGOs), and policy makers, as well as ten "leading" offshore wind developers and operators, it stated.
Tennet, Energinet, Gasunie and the Port of Rotterdam's hub is not the only proposed linking of North Sea countries with artificial islands.
The Centre for Electric Power and Energy at the Technical University of Denmark (DTU) is leading a research project to determine the technology needed for an artificial island to connect North Sea wind farms to surrounding countries.
And the UK’s Oil and Gas Authority is exploring the potential for creating artificial islands on which wind-generated electricity and hydrogen can be produced.