The transition to net-zero energy systems can only happen if offshore wind is massively deployed around the world. In Europe, the ambitions related to offshore wind development are quite high, aiming at 120 GW by 2030 and more than 300 GW by 2050 in the North Seas, an immense leap from the existing 30 GW.
As the development moves forward, the offshore wind projects are increasingly moving away from the coastline, while the onshore landing points for the grid connection are becoming more scarce and the projects are getting larger—frequently exceeding GW scale. Most of the offshore wind is connected to the onshore systems via high voltage alternating current (HVAC) lines today, the same as for onshore systems. When the distance from shore gets into high tens (or more) of kilometers, the technology used for the export system will move towards high voltage direct current (HVDC). With the rolling average distance of offshore wind projects in North Seas approaching 60 km, the grid connection of offshore wind is entering into a new phase of development.
This new phase of development for offshore wind grid connection translates into the development of the so-called energy islands, although energy hubs may be a more suitable term. In 2020, the Danish Parliament decided to develop and build two energy islands: one on the natural island of Bornholm in the Baltic Sea and a second as an artificial island in the North Sea. Both projects are very ambitious, but the North Sea Energy Island is particularly so. When completed, it will be one of the largest energy hubs in Europe, with a target of 10 GW installed capacity in the long term (double the 5 GW of the largest power plant operating today in Europe).
The sheer scale of these projects, combined with the ambition from Belgium and other European countries of building similar energy islands/hubs, makes them the equivalent of a Mars Mission for offshore wind and the energy system.
The Offshore Challenge
One particular challenge in the development of the energy islands is to design and build an electrical infrastructure that can operate with 100% renewable electricity. Each energy island will be an “electron metropolis” where electrons charged by offshore wind’s kinetic energy move through grid lines. They will be traded on markets by multiple vendors and eventually reach the mainland to directly power consumers or to separate molecules in power-to-X systems and green fuel technologies. These electron metropolises will have to operate systems of generating, selling, and transporting gigawatts of electricity with milliseconds of precision. Unlike traditional power systems, a 100% renewable system powered by wind does not have any system inertia to help balance the grid if energy supply suddenly drops. New solutions will have to be developed and matured to enable this.
From an electrical perspective, an energy island/hub is a unicorn of the fully decarbonized power system of the future. Its electrical infrastructure will consist solely of inverter-based resources, representing an electrical system with very little or even no directly connected mechanical mass. While the technology to build such a system is largely available today as individual components, combining them into a system of the scale of the energy island raises challenges at every step: how to design it, how to operate it, how to integrate it and how to expand it in a safe, seamless, robust, and efficient manner.
The Offshore Opportunity
However, with big challenges come great opportunities. Moving into the new era of offshore wind development allows for increasing awareness and understanding of the green transition. The energy islands/hubs are concrete and easy-to-visualize examples of energy transition and provide an invaluable opportunity to understand how to design, build, and operate an “extreme” power system. Designing and building the energy island/hub is also a unique opportunity to learn. It will provide the foundation for training engineers, technicians, regulators, and businesspeople in how to create a decarbonized energy system. This should be done through research and development at lab scale and in demonstration projects supporting the technology and service development.
Combined, the energy islands/hubs offer a unique opportunity for companies to develop innovation technologies and services; for politicians, regulators, technology providers, and system operators to develop the framework required to run the energy islands; and for universities and research organizations to research and develop completely new solutions. These new developments will be used for the energy islands and beyond, to educate the engineers to implement them and share knowledge with the world to advance the green transition around the globe.
Nicolaos A. Cutululis
Professor, Technical University of Denmark (DTU)