Ahead of schedule, Jan De Nul’s offshore jack-up installation vessel Vole au vent has completed its mission on the Saint-Nazaire Wind Farm project in France. The ship transported and installed eighty sets of 6 MW wind turbine generators for the very first commercial wind farm in French waters.

The Vole au vent loaded the 6 MW wind turbines, in sets of four, at the “Forme Joubert” lock in the port of Saint-Nazaire and then transported the components approximately 12 kilometres offshore for installation on top of the foundations located on the Banc de Guérande seabed, in the northern part of the Bay of Biscay.

On 1 April, the first turbine was loaded in the port. On 5 September, the eightieth and last turbine was successfully installed. By the end of 2022, the wind farm will have a total capacity of 480 MW.

‘The Saint-Nazaire wind farm is a milestone project for Jan De Nul, as this is France’s first offshore wind farm,’ says Pieter Vandezande, Project Manager at Jan De Nul Group. ‘We are proud to support the country in its energy transition by making possible the delivery of the first electricity produced by the very first French offshore wind farm. The exceptional installation progress has been the result of an extensive engineering process, optimised vessel preparation and planning, and an excellent collaboration with Parc éolien en mer de Saint-Nazaire and the turbine supplier GE.’

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Challenging soil conditions

Jan De Nul brought its dredging and offshore wind installation expertise together to develop a unique method of construction consisting of preparatory rock fragmenting operations.

The majority of the Saint-Nazaire turbines needed to be installed on an uneven rocky seabed. Since the self-elevating jack-up vessel Vole au vent needs a stable seabed to safely jack on, some additional rock fragmenting operations were required to prepare the seabed for jacking.

In the summer of 2021, Jan De Nul’s ocean-going cutter suction dredger Fernão de Magalhães performed these preparatory works. The dredger fragmented the seabed using its rotating cutter head to smooth the seabed that then allows the Vole au vent to perform jacking activities.

Picture: Jack-up vessel Vole au vent installing the last turbines on France’s first commercial-scale offshore wind farm in Saint-Nazaire.

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