Offshore wind hit a milestone this month with the announcement of the U.K.’s first decommissioning project.

Experts said the decommissioning due to take place on the Blyth plant would not yet open the floodgates for further end-of-life work, as most other offshore projects won’t shut down for almost a decade. But Blyth's retirement does offer a view into how the decommissioning process works. 

The decision by plant owner E.ON to cease operations at Blyth “will have little impact on the wider context, predominantly because this was a pilot site,” said Mike Mahoney, head of wholesale and modeling at London-based analyst firm Cornwall Insight.

Under the country’s Renewable Obligations scheme, the first commercial offshore wind plants in the U.K. were given a subsidy that is due to last until 2028. “It is unlikely that any further retirements are expected before this,” said Mahoney.

Blyth, which comprises two Vestas V66 2-megawatt turbines off the coast of Northumberland in northeast England, was commissioned in December 2000 by a consortium made up of E.ON, Shell Renewables, Vattenfall’s Nuon and Border Wind.

Although far from being the oldest offshore wind farm in the world (an honor that belongs to Denmark’s Vindeby project, which was finished in 1991 and decommissioned in 2017), Blyth marked the beginning of the industry in the U.K.

Britain subsequently went on to lead global offshore wind installations by a significant margin. And although in absolute capacity terms the country is now being overtaken by China, it still has plans to get more of its energy supplies from offshore wind than any other country.

“Blyth ushered in a new era of renewable technologies,” said E.ON in a press release. “As an offshore wind pioneer, E.ON used this example to lay the foundation for the future of the technology. It has undergone rapid development.”

Since commissioning Blyth, E.ON alone has installed a further 600 offshore wind turbines in the seas of northern Europe, the company said. Given the size and maturity of U.K.’s offshore wind market, it is likely the country will be the first to perfect plant decommissioning at scale.

And Blyth could offer insights into how that might happen.

The decommissioning process

E.ON said the dismantling work would start in April and is expected to take four to six weeks.

One of the turbines will be recycled and reused for spare parts within E.ON's onshore fleet, and the other will be used for training purposes by the Port of Blyth, E.ON said.

The plant has had a shorter lifespan than most commercial projects now in operation, said E.ON spokesperson Markus Nitschke. The usual lifespan is 20 years, although more recently that has frequently been extended to 25, he said.

Decommissioning is required by the permitting authorities, he noted. When the turbines are taken down, some components will be used for the maintenance of other wind farms and other parts will be recycled. “There might be some waste as well, but not much,” Nitschke said.

The decommissioning isn't expected to be a technically challenging process. Although E.ON is not releasing the cost for dismantling Blyth, Nitschke said that it was essentially similar to building the project, “just the other way around.”

The industry has “sufficient competencies” to handle the work, he said.

Repowering not an option offshore

What doesn’t appear to be in the cards for future offshore wind farms reaching end of life is repowering. 

Replacing old turbines with newer, more powerful models is a popular strategy in onshore wind, but it doesn't work well offshore because of the rapid evolution of the turbine technology.

Across the country from Blyth, for example, each of the 8.25-megawatt MHI Vestas turbines recently installed at Ørsted’s Walney Extension project has a capacity more than double that of Blyth’s entire output. 

Putting one of these monsters onto the foundations installed at Blyth simply isn’t an option.

Instead, said Mahoney, “as part of planning and development for an offshore wind farm, the decommissioning requirements should include reusing or recycling the materials and equipment.”

That does not mean wind turbines won’t return to Blyth, however.

The U.K.’s ambitious offshore plans may put development-ready seabed areas at a premium, and “it might be economical to use the area to build a new wind farm with the latest technology,” said Nitschke.