The offshore wind sector is undergoing a significant transformation, and at the fore-front stands Hornsea 3 – the world’s single largest wind farm currently under construction. With a planned capacity of 2.9 GW, this project is more than just another milestone for Ørsted; it represents a defining moment in the renewable energy transition. As part of the broader Hornsea Zone, Hornsea 3 is set to become one of the world’s largest renewable energy installations, surpassing its North Sea neighbour and sister project, Hornsea 2.
A legacy of innovation: From Vindeby to Hornsea 3
Located 120 km off the Norfolk coast, this £8.5 billion project will feature 197 turbines spanning nearly 700 km2 – an area larger than Greater Manchester. Once operational, it will generate enough electricity to power over 3.3 million UK homes, making it a cornerstone of the country’s net-zero ambitions. To fully appreciate the significance of Hornsea 3, one must look back at how far offshore wind has come.
More than 30 years ago, offshore wind was an untested concept. Vindeby, developed by Ørsted in Denmark in 1991 and the world’s first offshore wind farm, consisted of just 11 turbines generating a modest total output of 5 MW – enough to power 2200 homes. At the time, the industry was in its infancy, but Vindeby crucially proved that offshore wind was viable.
Fast forward to today, and a single turbine at Hornsea 3 will easily surpass Vindeby’s total capacity. This progress highlights relentless advancements in turbine technology, engineering, and large scale project execution.
Yet, developing the world’s largest offshore wind farm is about more than just installing turbines – it requires the seamless integration of offshore and onshore infrastructure to deliver clean energy efficiently to the UK grid.
The backbone of Hornsea 3: Onshore infrastructure
When people think of offshore wind, they often picture vast arrays of turbines standing tall over the waves. However, what happens onshore is just as vital to a project’s success and is where the hard work begins – there are many moving parts to get right before offshore construction can start. The integration of large scale offshore wind farms requires sophisticated onshore infrastructure to ensure electricity reaches consumers efficiently and reliably.
Hornsea 3’s onshore infrastructure consists of several key components:
- Cable landfall: Subsea cables will make landfall near Weybourne, Norfolk, connecting to an underground onshore cable network.
- Onshore cable route: A carefully planned 55-km underground corridor through Norfolk, designed to minimise environmental impact and community disruption.
- Onshore converter stations: Two high-voltage direct current (HVDC) converter stations at Swardeston, south of Norwich, will convert power from HVDC to alternating current (AC) for efficient grid integration.
- Onshore substation: Also located near Swardeston, this facility will be where the electricity enters the National Grid.
The onshore phase of Hornsea 3 is well underway. Construction of the HVDC system began in 2022 and is progressing steadily. Steelwork and foundations for the converter stations are largely in place, and work on the HVDC valves will begin later in 2025. Meanwhile, trenching and tunnelling for the onshore cable route is advancing, with cables transported from Sweden via the Port of Boston in Lincoln-shire. The logistics are complex – cables must be cut to manageable lengths and transported under police escort to the site.
At Weybourne in North Norfolk, where the export cable will make landfall, preparations for the horizontal directional drill (HDD) have nearly been completed – utilising a jack-up barge, stationed 600 m offshore, to facilitate work on the connection between onshore and offshore cables. By early 2026, subsea cables will be pulled through, establishing the crucial link between the wind farm and the grid.
Harnessing the power of HVDC technology
Given Hornsea 3’s considerable 120 km offshore distance, it will be Ørsted’s first UK project to use HVDC technology, which is more efficient for long-distance power transmission.
In partnership with Hitachi Energy and Aibel, Ørsted is installing four HVDC converter stations – two offshore and two onshore – to convert electricity between AC and DC. The HVDC system, in development since 2022, adds an extra layer of technical complexity to the project.
Enjoyed what you've read so far? Read the full article and the rest of the Summer issue of Energy Global by following the link below, or why not register today for free!
For more news and technical articles from the global renewable industry, read the latest issue of Energy Global magazine.
Energy Global's Summer 2025 issue
Dive into the latest renewable energy insights in the Summer issue of Energy Global, out now! This edition features a guest comment from Change Rebellion on the role real change management can play in the global energy sector before a regional report, which looks at energy trends and transformations across the Americas. Other key topics are also explored, including offshore support vessels, floating wind, weather analysis, and battery storage. Contributors include Ørsted, CRC Evans, Miros, Solcast, and more, so don’t miss out!