Offshore wind farms have been built in UK waters since the early 2000s. Until now, these projects have all used ‘bottom-fixed’ designs, where the turbines are placed directly on the seabed. While there are several different approaches for bottom-fixed foundations, they can only be installed in relatively shallow waters, which usually means they are close to the shore.
Floating offshore wind technology will open up transitional and deep-water offshore wind sites around the UK that were previously inaccessible. This will help meet the UK’s Net Zero target whilst reducing the visual impact of the turbines and minimising interferences with local activities. It will also contribute towards revitalising coastal communities and create local jobs.
The swift development of Petroc will play a major role in the progression of a floating wind industry in the Celtic Sea, and will be instrumental as a stepping stone for larger developments by the end of the decade to help meet the 2035 4GW target. We are keen to continue working with The Crown Estate and the (local) development community to put in place a suitable regulatory framework that will allow projects like Petroc to be delivered in the second half of this decade.
Traditional bottom-fixed designs are not feasible in waters deeper than 60 metres. Floating offshore wind technology allows turbines to be installed in much deeper waters and further from the shore.
Because floating wind turbines can be placed further from the shore, they can also benefit from the stronger and more consistent winds that you can normally find further out to sea. Experience from early floating projects in the North Sea shows that this can lead to an improvement in capacity factor of 5-20% over conventional bottom-fixed turbines. In other words, the turbines are operating significantly closer to full capacity, which is more efficient, and represents better value for energy companies, and ultimately cheaper energy for consumers and businesses too.
By installing wind farms further offshore, the visual impact on local shoreside communities is significantly reduced. Petroc wind farm will be located 37 miles from land, minimising the visual impact of the development.
The mooring system of floating turbines also limits the risk of disruption to the seabed or marine ecosystems, compared to traditional bottom-fixed pilings. Due to being located further offshore, floating turbines also have less impact on other marine users, such as the fishing, shipping or tourist industries. Finally, at the end of the wind farm’s lifetime, the anchors are also easier to retrieve during decommissioning than the heavy foundations of bottom-fixed platforms.
Fixed-bottom turbines are assembled at sea, meaning their major components (blades, nacelles, towers, foundations) can be transported by ship from very far away and they do not need to employ local ports and other infrastructure for the installation and maintenance. Unlike bottom-fixed constructions, floating turbines are assembled onshore (at quayside), before being towed to sea to be installed. This means major economic opportunities for the local economies around ports and the local supply chain that need to service the construction and maintenance of floating wind farms.
Floating turbines have a lot in common with bottom-fixed turbines. Bottom-fixed designs generally are built directly on, or into, the seabed, using either a steel or concrete monopile or a legged ‘jacket’ (like a huge 3- or 4-legged stool attached to the seabed). The turbine and its tower sit on top of this monopile or jacket.
With floating turbines, the upper part of each structure is fundamentally the same. But instead of sitting on a fixed structure, the turbine is attached to a ‘floater’. This is a movable structure that provides the turbine with buoyancy and stability, to keep it upright at all times. This floater is then secured to the seabed using mooring lines and anchors for station keeping.