Heerema’s Thialf Lowers Seagreen Topside Into Place

The 4,800-tonne offshore substation topside has been installed at the 1,075 GW Seagreen wind farm offshore Scotland.

At 40 metres long, 45 metres wide, and 15 metres high, the topside will collect and manage the power generated by the 114 Vestas 10 MW wind turbines before transferring it ashore via around 60 kilometres of offshore subsea cabling.

Source: SSE Renewables

Once onshore, the electricity continues to the new Tealing substation near Dundee via a further 19 kilometres of cabling for onward distribution to the Scottish homes and businesses via the national electricity network.

The topside was lifted from Heerema Marine Contractors’ heavy transport vessel, Thialf, and on to the previously installed six-legged jacket foundation.

The completed structure sits in water depths of around 55 metres and will be one of the largest AC platforms in UK waters, SSE Renewables, the developer of the project said.

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Specialist cable installation and support vessels will continue to install the onsite inter-array network of cables to the turbines and to the offshore platform.

Another vessel is currently installing the export cable from the landfall point at Carnoustie.

”Once again, the many years of careful design and planning have come to fruition with the arrival and successful installation of one of the UK’s largest offshore AC platforms, serving what will become Scotland’s largest offshore wind farm,” Director of the Seagreen Wind Farm Project, John Hill, said.

”At around 4,800 tonnes, the topside is a significant piece of equipment which has been carefully designed to withstand the rigours of a long operational life in the North Sea. The teams involved have done an excellent job.”

Petrofac is in charge of the installation work under a contract the company was awarded for the design, supply, and installation of the High Voltage Alternating Current (HVAC) onshore and offshore substations for the 1,075 MW offshore wind farm.

”The safe and successful installation of the substation topside is a significant milestone in the delivery of this important energy transition project for the UK. Everyone involved should be proud of this achievement and the great teamwork and collaboration shown between all partners and parties working together,” Vipul Sawe, Petrofac’s Senior Project Director said.

Situated around 27 kilometres off the Angus coast, the Seagreen wind farm is a joint venture between SSE Renewables (49 per cent) and TotalEnergies (51 per cent).

SSE Renewables is leading the development and construction of the Seagreen project and will operate Seagreen on completion for its expected 25-year lifetime.

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The wind farm is scheduled to enter operation in early 2023. At 1.1GW, the wind farm will be capable of generating around 5,000 GWh of renewable energy annually which is enough electricity to power more than 1.6 million UK homes.

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Photo: SSE Renewables