Wind

Why flagship Subsea 7 vessel will play a limited role at giant Dogger Bank offshore wind

Installation of foundations has remained ahead of schedule at world's largest project despite shipyard 'crane incident' that set back delivery of Alfa Lift

The Seaway Strashnov wind vessel has stood in for its bigger cousin on Dogger Bank
The Seaway Strashnov wind vessel has stood in for its bigger cousin on Dogger BankFoto: Courtesy of Seaway 7
Olso-based offshore contractor Subsea 7 is to put its new Seaway Alfa Lift offshore wind foundation installation vessel to work on SSE’s flagship Dogger Bank by the end of this year, but with a more limited role than originally envisaged following agreement on a revised execution plan with developers.

The semi-submersible heavy installation vessel will join Subsea 7's fleet in the third quarter of 2023.

It was built at China Merchants Heavy Industry (CMHI) shipyard in Jiangsu, China and was originally earmarked to carry out foundation installation operations on SSE’s flagship Dogger Bank wind farm.

However, delivery from the Chinese shipyard was delayed by a crane incident there in October 2021 and Subsea 7 has instead deployed the Seaway Strashnov vessel to keep the Dogger Bank project on track.

In its earnings update at the end of July, Subsea 7 reported that 71 of Dogger Bank A’s 95 monopiles have been installed and that it was “on track” to complete this scope in the third quarter of 2023, and finish the transition pieces in the fourth quarter, ahead of the original schedule.

Last week SSE reported that work to install the first wind turbine at the UK’s Dogger Bank – on course to be the world’s largest offshore wind farm – was set to begin "within days."

Project partners SSE, Equinor and Vargronn said the installation of the first of the 277 13MW GE Haliade-X machine was expected to get underway at the weekend with Belgian contractor Jan de Nul's Voltaire vessel on its way with the turbine components.

Dogger Bank will when fully built-out at a cost of some £11bn ($14bn) have a capacity of 3.6GW and supply, making the project a new benchmark in the ambition of the global offshore wind sector.

The imminent arrival of the Seaway Alfa Lift in European waters could still contribute to the overall foundations work, although under a new plan for Dogger Bank B & C.

The vessel set sail from China last month and remaining mission equipment will be completed and commissioned Europe, according to the vessel’s designer Ulstein.

Bigger, better... but not yet

It has a 3,000-tonne capacity main crane and will eventually be able to handle bigger foundations and transition pieces for higher overall efficiency than the smaller Strashnov.
Quizzed about the role of the Seaway Alfa Lift on Dogger Bank, Subsea 7 chief executive John Evans told analysts on a recent earnings call that the “steady and predictable cycle times” achieved by the Seaway Strashnov on each monopile had helped convince SSE to agree to a revised execution plan.
Under that plan, the Seaway Alfa Lift vessel will be deployed on transition piece installation on Dogger Bank A & B and C from late 2023 to 2025, while monopile installation will continue throughout the period with Seaway Strashnov.

“A strong performance on Dogger Bank A will allow commencement on Dogger Bank B, and we expect to start installing monopiles in the third quarter of this year. The remainder will be installed in 2024 as planned," Evans said.

The Subsea 7 CEO explained that the Seaway Alfa Lift still has some mission equipment for under construction ahead of foundation monopile installation.

"The mission equipment for Seaway Alfa Lift remains under construction but is now removed from the critical path," Evans said, describing the move as a strategy to "derisk" Dogger Bank.

Stuart Fitzgerald, CEO of Seaway 7 added: ""We would not intend to install that mission equipment ahead of.. the 2024 campaign. We focused the vessel on transition pieces, and we see acceptable returns on the vessel investment in that mode, given these transition pieces are large and it is relatively high spec work."

Financing vessels

Subsea 7 also said it was in the process of concluding a $450m debt funding exercise to help conclude the construction and commissioning of the Seaway Alfa Lift and the Seaway Ventus heavy-duty jack-up vessel suitable for turbine and monopile installation, which is due for delivery at the end of 2023.

The Ventus is booked to carry out wind turbine installations on Germany’s Borkum Riffgrun 3 and Gode Wind 3 wind farm projects in 2024 and on monopile installations on the UK’s East Anglia 3 project in 2025.

(Copyright)

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Published 7 August 2023, 05:35Updated 7 August 2023, 05:35
Dogger BankSeaway 7Subsea 7SSEUK