Tahkoluoto, Finland's first commercial offshore wind farm, photographed from a vessel

Finnish developer probing seabed at extension site of world’s first offshore wind farm in freezing conditions

Suomen Hyötytuuli has performed test dredging at the site of the Tahkoluoto offshore wind farm extension project, where the company plans to build a 600+ MW expansion to the existing 44.3 MW offshore wind farm, the world’s first built and operating in frozen sea conditions.

The test dredging was carried out in early May to test suitable methods for building the offshore farm at the site located between 4 and 22 kilometres off the coast of Pori at the Sea of Bothnia.

The Tahkoluoto offshore wind farm’s extension is planned to comprise 40 wind turbines of more than 15 MW capacity each, installed at a depth of up to 40 metres.

“The test dredging has provided valuable information about the quality of the seabed of the Sea of Bothnia and about the suitable equipment and methods for dredging in the area. It has also provided insight as to how deep the dredging needs to go in order to establish sufficiently robust foundations for the offshore wind turbines cost-efficiently and in compliance with the criteria,” Suomen Hyötytuuli said in a press release on May 13.

The latest test work follows the site investigations launched last year, when the Dutch-Finnish consortium Boskalis-Terramare and the Finish Hyötytuuli performed seabed test excavations at a depth of 43 metres.

The construction of the extension offshore wind farm is expected to take place in 2027–2029, with the wind farm’s total capacity planned to be between 600 MW and 800 MW.

The two-turbine demonstration project, which will put the larger-scale offshore wind turbines to the test in freezing conditions, will be built first.

The pilot project will also demonstrate a foundation concept for deep waters in frozen sea conditions, significantly deeper seabed installations and seabed building methods appropriate for these conditions, according to the developer.

The demonstration project was granted building and water permits in December 2023.

The European Union has granted the demonstration project funding under the NextGenerationEU recovery instrument, according to Suomen Hyötytuuli.

The Finnish developer said this March it would conduct a full demerger that would see its wind farms, including the existing Tahkoluoto offshore wind farm, transferred to a new firm of the same name, while Tahkoluoto Offshore Oy would take ownership of the new Tahkoluoto demonstration and extension project.

The demerger process, initiated with the filing of the plan with the Finnish Patent and Registration Office on March 8, is scheduled to be completed by the end of Summer 2024.