It verified that the fasteners suffered no corrosion, wear or galling after two years of operation in extreme conditions.
The Bumax premium stainless steel fastener solution has been verified by a two-year pilot project that has contributed to the development of the next generation tidal turbine, capable of providing Europe with reliable renewable energy.
“This is extremely encouraging for the future of sustainable renewable energy solutions, since wear and tear and maintenance are major challenges for power plants in extreme conditions like choppy and salty waters with strong currents,” said Lars Holm, managing director of Bumax. “Europe also needs to develop new sources of reliable renewable energy, which this project will lead to.”
Bumax 88 fasteners were used on the 1 MW HydroQuest tidal turbine installed off the coast of Brittany in Northwest France that began operation in April 2019. After over two years of operation at the Paimpol-Bréhat site at 30m depth, the turbine fasteners showed no traces of corrosion or galling.
Tests of the mechanical properties (both strength and ductility) of the bolts conducted by Bumax after the pilot project showed that they had maintained their properties.
“No issues were found related to bolting during this project, and our team didn’t have any issues with galling during disassembly,” said Raphaël Coquet, project director at Hydroquest. “These lessons give us positive learnings for the long-term deployments, and we are confident to manufacture our future turbines with Bumax bolts.”
The Bumax 88 grade, which uses 316L grade stainless steel, was selected for its high molybdenum content and high pitting resistance equivalent number (PREN) which indicates a high resistance to localized pitting corrosion, Bumax said.
The tidal turbine prototype was designed by HydroQuest, which is a French turbine technology developer of vertical axis turbines. The Paimpol Bréhat site is owned and operated by the energy company EDF.
The project partners wanted a maintenance-free fastener solution for tidal turbines to minimse operation costs over a lifespan of 20 years. Besides durability, the fasteners also had to be easy to install.
Following the pilot project at Paimpol Bréhat, HydroQuest is integrating the learnings from the pilot to design the next generation of tidal turbine, which will also use Bumax 88 bolts.
Seven of these 2.5 MW tidal turbines will be deployed at the FLOWATT project at the Raz Blanchard site off the coast of Normandy with a design lifespan of 20 years. The commissioning of FLOWATT is planned for 2025 with the construction of the tidal turbines starting in 2023.