Saint-Nazaire offshore wind farm substation: speedy construction with ArcelorMittal steel and technical support

Chantiers de l’Atlantique is best known for building some of the world’s largest cruise ships. Around a decade ago, the company decided to diversify and began building substations for offshore wind farms. At first glance it might seem that ships and substations have little in common, but the reality is that both require exceptional planning, detailed knowledge, and the ability to turn tonnes of ArcelorMittal steel into vast structures which can withstand the harsh environment of the open ocean. One of the substations built by Chantiers de l’Atlantique was installed in August 2021 and services the Saint-Nazaire offshore wind farm. The wind farm is operated by EDF, France’s largest energy provider. This is the fourth Chantiers de l’Atlantique substation for which ArcelorMittal has provided steel.

Detailed information

Similarities between substation and ship construction

“In terms of project management and the integration of equipment, there are many similarities when it comes to building ships and substations,” notes Yann Penduff, project manager for Chantiers de l’Atlantique. “For example, we use the same modular approach to construction and many of the same technologies for both applications.”

“Power transformation and distribution, which are also the main functions of a substation, are an integral part of shipbuilding,” explains Yann Penduff.

The substations are built from both normalised and thermo-mechanical grades from ArcelorMittal Europe – Flat Products. “The steel has specific chemical and mechanical properties,” says Serge Hily, steel purchasing manager for Chantiers de l’Atlantique. “It also exhibits excellent welding properties.”

Substation construction with ArcelorMittal staff on site

ArcelorMittal delivers plates for both ships and substations every two weeks by sea from its mill in Gijon, Spain. “We can adjust the volumes as required,” explains Serge Hily. “If more steel is needed urgently, the mill is close enough to allow deliveries by road.”

To facilitate quick communication on this project, ArcelorMittal deployed a technical engineer and an R&D specialist to Chantiers de l’Atlantique. “The presence of the ArcelorMittal personnel enabled us to get fast responses to technical questions,” says Serge Hily. “It really accelerated the dialogue between the technical teams. This was critical given the small timeframe available.”

The mammoth substation structures made for EDF are 20 metres high, 20 metres long, and 30 metres wide. Each one weighs around 2200 tonnes.

Innovative corrosion resistance solutions for offshore environments are key

Chantiers de l’Atlantique paints or treats every piece of steel in the substation to withstand the corrosive offshore environment. “ArcelorMittal R&D has developed many innovative corrosion resistance solutions for use in marine environments,” notes Laurent Castro, ArcelorMittal account manager for Chantiers de l’Atlantique. “This work continues in cooperation with customers such as Chantiers de l’Atlantique.”

Once it is painted, the substation is fitted out with the technology needed to transform energy from the wind farm and transfer it to shore.

One of the biggest challenges Chantiers de l’Atlantique faces when building substations is the tight deadlines. “There are very few vessels available to install substations at sea,” notes Yann Penduff. “We must book the vessel three years in advance, and then we have just one week to install the substation on its foundation. That requires clockwork precision from our team and our suppliers.”
A specialised ship lifts the substation into place onto a jacket or monopile which has already been installed.

The Saint-Nazaire substation was installed in August 2021. Since April 2022, it has been fully operational, transmitting around 480 megawatts of electricity produced by 80 turbines to shore. The wind farm generates around 20 per cent of the energy consumed by France’s Loire-Atlantique department which is home to over 1.4 million people.

ArcelorMittal’s offer for wind energy and shipbuilding

ArcelorMittal Europe – Flat Products can supply offshore and shipbuilding grades with very high strength and toughness. Plates are available in widths up to 3.3 metres with a tensile strength of up to 460 Mpa. The maximum weight of a single plate can be up to 19 tonnes. ArcelorMittal is actively working to increase the thickness range of its plates for wind energy and shipbuilding. The dimensional feasibility of ArcelorMittal’s offer reduces the number of welds required, reducing costs and production time significantly.

Like all ArcelorMittal steels, the offer for wind energy and shipbuilding is available with XCarb® green steel certificates which enable customers to reduce their Scope 3 emissions. ArcelorMittal’s XCarb® initiative brings together all of our reduced, low, and zero-carbon products and steelmaking activities, as well as wider initiatives and green innovation projects, into a single effort focussed on achieving demonstrable progress towards carbon neutral steel.

About Chantiers de l’Atlantique

Chantiers de l’Atlantique is a shipyard in Saint-Nazaire, France which was first established in 1861. The shipyard was acquired by a number of companies over the years before becoming independent in 2018.

As well as building cruise ships and naval vessels, Chantiers de l’Atlantique builds substations and other equipment for the renewable energy sector. The company also offers a range of services to the owners of civilian and naval fleets.

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Project information

  • Saint-Nazaire
  • France
  • 2022
  • Contractor:
    Consortium of Atlantique Offshore Energy (Chantiers de l’Atlantique), GE Grid Solutions, and SDI (DEME Group)
  • Developer:
    EDF Renouvelables and EIH S.à r.l
  • Text:
    ArcelorMittal Europe - Flat Products
  • Photos:
    © Chantiers de l’Atlantique