Early wind turbine deployments are reaching the end of their operational life, a new industry is evolving to decommission and, in some cases, to recommission these sites.

The UK Government, the world’s second largest offshore wind farm operator after China, has announced it intends to decouple renewables from ‘gas-linked’ energy prices. A move to a contract-for-difference (CFD) model, will allow renewables to undercut gas powerplants when selling to the UK grid.

That shift will incentivise a further buildout of offshore wind farms, including, crucially, to ‘re-power’ old wind farm sites.

This has already happened at the site of the UK’s first offshore installation, the Blyth Offshore wind farm, where two Vestas 2MW offshore turbines were installed in 2000, were decommissioned in 2019, and subsequently replaced with five turbines generating 41.5MW – an increase of almost 2,000%.

“Repowering presents a major opportunity to fully utilise the UK’s limited seabed space,” said a 2025 report, Developing effective end-of-life policy frameworks for UK offshore wind­, by Renewable UK.

Although “Repowering… decommissioning and recommissioning… has a cost profile that is similar to that of a new build project,” the report noted, as repowering sites compete with greenfield farms for offshore vessel capacity – which do not need to haul away their old turbines first.

Supply is constrained, with existing wind turbine installation vessels (WTIVs) capable of 15MW or greater, experiencing 70-80% utilisation, according to offshore maritime operator Spinergie.

In The Netherlands the port of Amsterdam is positioning itself as an offshore hub, with AYOP, an offshore energy network of businesses promoting the regional industry. AYOP director, Dionne Ruurda, explained that reusing old sites can be a challenge with the earlier turbines requiring smaller foundations.

Much larger modern turbines require a considerably larger base so reusing older foundations is not an option, while removing them is a challenge yet to be adequately met, according to Ruurda.

Many offshore wind assets –necessarily installed in the most attractive and productive sites –are approaching the end of their 25-year lifespans.

Denmark’s Tunø Knob and Middelgrunden wind farms, installed in 1995 and 2000 respectively, are both situated in water less than 6m deep, meaning that a relatively short-legged jack-up can be used – though it is much more likely to be one of many self-propelled Danish jack-ups in the Ziton or Cadeler fleets.

The question of how best to decommission turbines, and what to do afterwards, poses a conundrum that from the perspective of ship designers and builders, needs to be settled soon.

It becomes more pressing as installations move into deeper water – Denmark’s Samsø, and the UK’s Horns Rev 1 and North Hoyle, all installed before 2004, are likely next in line for decommissioning, and all are situated in water depths of around 10m. More recent installations will require more robust jack-ups, with longer legs and better seakeeping.

Cabling is another issue. Older offshore wind installations tend to have some additional complexity in store for decommissioners. In a 2016 study, Down to the Wire: An Insurance Buyer’s Guide to Subsea Cabling Incidents, GCube, an underwriter for renewable energy, highlighted that a frequent cause of damage to cables arose from installers laying them on top of one another. Lift one for repair, and it would sever another.

During the early era, cable and ROV surveys were not a requirement – so, were not routinely used. “Cable installation techniques and monitoring technology are continuing to evolve as the industry looks to address this challenge,” wrote GCube head of business development Jatin Sharma. “However recurring losses are still commonplace and is a source of concern for the insurance industry.”

Another insurer, Lloyd Warwick, found that 83% of offshore wind claims had to do with cables. UK offshore renewable energy innovator, Catapult, estimates 46% of all power cable failures result from damage incurred during installation.

In this context, the decision to just leave turbines or their foundations where they are makes a degree of sense. For campaign group Seas at Risk, it could even be a good thing. Disused turbine monopiles serve to anchor the seabed against tidal erosion, protecting local ecosystems.

In addition, “We noticed that ‘new nature’ developed because of the artificial reef effect coming from the hard substrate introduced in that environment,” explained Nele Desplenter. Attaché for Belgium’s Marine Environment Department, during a recent seminar.

She added: “This is not a naturally occurring biodiversity at that location – so there is a lot of discussion on the value of this new nature that has not been clarified.”