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STX France Saint-Nazaire, building offshore substations

Construction Navale
Energies Marines

STX France Saint-Nazaire, world famous for its cruise liners, is diversifying into marine renewable energy, specifically substations for offshore windfarms.

Two substations are currently under construction. Project Q34, just begun, is a 309-MW substation (topside, foundation and piles) ordered by the Otary consortium for Belgium’s Rentel windfarm which will comprise forty-two 7-MW Siemens turbines. Project P34, is more advanced. This huge 385-MW substation, among the biggest in the world, is for the Arkona windfarm, comprising sixty 6-MW turbines, being developed by German power utility E.ON and Norwegian group Statoil. The P34 topside will weigh 4,000t, compared with 1,200t for Q34. Both substations are scheduled for delivery in 2018.

 

The Q34 substation (© STX France)

 

Q34 and P34 are being built at the Anemos complex, opened by STX France in 2015 and recently extended to accommodate a growing workload. This 12,000sq.m facility was purpose-built to produce heavy structures for MRE projects.

The fabrication shop is 35m wide by 16m high and was recently extended from 90 to 120m in length. With two 60t gantry cranes, it is used primarily to fabricate topside blocks. Work then moves to a 6,000sq.m assembly & outfitting area located between the fabrication shop and the paint hall which is 50m long, 35m wide and 25m high and among the biggest of its type in Europe. The paint hall’s controlled atmosphere is maintained at a steady 18°C and 55% RH. Topside blocks are transferred one at a time from the fabrication shop to the assembly & outfitting area, then to the paint hall. Substation P34 comprises three blocks. The first was in the paint hall when we visited. Each structure is shot blasted before receiving successive protective coatings.

 

A Q34 block in the assembly & outfitting area (© Mer et Marine - Vincent Groizeleau)

Fabrication hall (© Mer et Marine - Vincent Groizeleau)

STX France’s Anemos plant (© Bernard Biger - STX France)

 

This coming summer, the barge that will take substation P34 to the Arkona windfarm will be in a building dock on the Anemos site. STX France will then assemble the P34 topside and jacket foundations directly on the barge. The Q34 substation is different in that it calls for monopile foundations which will be fabricated by a company in the Netherlands.

These contracts confirm the growing success achieved by the Saint-Nazaire yard in this promising new market. “Today, in MRE, we’re booking orders while preparing bids for future work. This is a promising market for Europe and our first projects have demonstrated that we are both competitive and innovative. This is precisely why we chose to invest in our new plant and facilities, effectively making Saint-Nazaire a benchmark location for MRE,” says Laurent Castaing, CEO of STX France.

 

The P33 substation during delivery to Dong Energy in 2014​​​ (© Bernard Biger - STX France)

 

In 2012, shortly after the company had decided to diversify into MRE, STX France won a contract, awarded by Danish windfarm operator Dong Energy, to build a substation for the British Westermost Rough field comprising thirty-six 6-MW turbines. Substations like these receive low-voltage power from turbines then transform it to a higher voltage for transmission ashore over a single HVAC or HVDC submarine power cable. Substation P33 was delivered in the summer of 2014. The topside weighs 1,450t, including 700t of electrical equipment, and is 16m high with a base measuring 31m by 18m. The jacket weighs 1,100t and is 38m high. It is mounted is on a square base measuring 32m x 32m. Once installed, the lower 20m of the jacket will be below the surface.

 

P33 topside ​​​​​​​(© Bernard Biger - STX France)

 

This project enabled STX France to hone its skills in a range of specialised areas that differ markedly from the yard’s established expertise in shipbuilding. In addition to withstanding the enormous forces of the North Sea’s severe weather, huge seas and high winds, the structure supporting the electrical equipment must be extremely reliable. “Only a handful of European companies can handle projects this challenging. This kind of work demands advanced know-how, proven expertise in welding, experience in handling and assembling special steels and other high-quality materials, and coatings to the highest standards to withstand offshore conditions. In other words, the very best in large offshore structures,” says Frédéric Grizaud, head of STX France’s Offshore Energy Business Unit.

 

​​​​​​​​​​​​​​(© Bernard Biger - STX France)

 

To fabricate P33, STX France worked with steels with an average thickness of 40mm and in some instances up to 100mm. These heavy-gauge products are very different from the comparatively thin sheet steel, between 10 and 15mm, used for the cruise liner hulls. Electrical substation platforms are also extremely complex with dozens of steel tubes intersecting each other, each having to be cut to extremely close tolerances before welding. The yard assigned its most experienced welders to the task and also gave them task-specific training. “The welding procedures for this type of work are very demanding, with tighter specifications than the projects we normally work on. Fortunately, we have some very talented welders at Saint-Nazaire who, with some additional training, proved fully up to the task.”

The construction of P33, followed by its successful installation and commissioning, paved the way for more MRE projects and the decision to invest €20 million in the Anemos plant. This highly automated facility is designed specifically to produce structures for MRE projects using innovative procedures that have improved productivity and reduced costs.

 

Frédéric Grizaud, head of STX France’s Offshore Energy Business Unit​​​​​​​ ​​​​​​​​​​​​​​(© Mer et Marine - Vincent Groizeleau)

 

STX France has long worked closely with key subcontractors. For these MRE projects, the company encouraged them to improve their organisational and engineering skills to meet the demanding new requirements. “Broadly speaking, our approach is inspired by the way we build ships. The core skills are engineering, complex project management and fabrication methods followed by commissioning and delivery. For other skills, like painting and coatings, pipework and insulation, we rely on subcontractors who are committed to continuous improvement at the company level and for all employees. Overall, we’re working as a team to develop our skills in this new area of expertise.” Electrical equipment also demands special expertise. As with other areas, STX France is working closely with specialised contractors, notably Schneider Electric for P34 and GE Grid Solutions for Q34.

 

(© STX France)

 

In parallel with these project activities, STX France has set up a specialised MRE engineering department and invested heavily in R&D. Indeed, these commitments have resulted in innovations for the substations proper and their foundations. Again, the payoff comes in the form of lower costs. Whereas the basic design for P33 was developed by Dong, STX France also did the design work for subsequent projects. Indeed, the company’s high-efficiency plant and technological innovations have put it ahead of most of its competitors to the point where Saint-Nazaire is now seen as a leading challenger. “STX submitted a strong, competitive bid. Given the company’s expertise in engineering and project management, and its recent investment in a dedicated plant, we are confident that it has the necessary know-how and will successfully complete the project,” said Rentel CEO Nathalie Oosterlinck, when placing the order for the Q34 project in early 2016.

STX France won the Q34 contract ahead of seven European competitors. The Q34 and P34 contracts are the first two EPCI (engineering, procurement, construction and installation) contracts the company has won.

 

STX France’s Anemos plant ​​​​​​​​​​​​​​(© Bernard Biger - STX France)

STX France’s facilities ​​​​​​​​​​​​​​(© Bernard Biger - STX France)

 

Over the last three years, STX France, which already employs over 2,600 people, has hired 150 new recruits to work on MRE projects. A further 150 or so employees of STX subcontractors also work at the Anemos plant. While the company awaits the outcome of bids to work on several other European projects, the management team also anxiously awaits the start of production work, scheduled to begin in 2018, for France’s first offshore windfarms. So far, the government has awarded contracts for six windfields off the country’s Atlantic and Channel coasts representing some 3000 MW.

STX France has also expressed keen interest in the calls for tenders, anticipated in the early 2020s, for floating offshore wind turbines and commercial tidal turbines.

Translated and adapted by Steve Dyson

 

​​​​​​​​​​​​​​(© STX France)

 

STX FRANCE (Chantiers de Saint-Nazaire)