A trio of offshore contractors has unveiled a new three-legged turbine foundation that targets taking bottom-fixed wind power projects far beyond the 30-50 metres water depths historically seen as the limit to the economics of ultra-large monopile and jacket designs.

Sif, KCI and Smulders are aiming at a ‘revival’ of the tripod concept deployed offshore at Global Tech 1 windfarm in the early 2010s, but soon after abandoned as uncompetitive with the low-cost monopiles used in that era.

The new design is angling at “its own specific niche” say the companies, pointing at the 60-70 metres water depth that is out-of-reach for even XXL monopiles.

“Times have changed and with bottom fixed foundations being deployed at ever greater water depths in the northern North Sea basin, we now see monopiles being selected up to 50-60 meters of water depth and jackets as the complementary foundation of choice from those or greater water depths,” said Sif’s Michel Kurstjen.

The piled-in tripod is engineered to have “specific advantages” over bottom-fixed foundations being of “sturdier construction than a monopile and easier to manufacture than a jacket”, he added.

Manufacture of the design will take place across several sites, with the central column fabricated at Sif’s factory in Roermond, the Netherlands, bracings sourced from a number of UK suppliers, and final assembly at the Smulders Wallsend site in England. Serial production is slated to start in 2024.

“The tripod design… is the second innovation next to our Skybox design that we have developed since Sif’s acquisition of KCI,” noted Kustjen. “With ever larger diameters of monopiles, the balance is now shifting from our Roermond facility to our Rotterdam facility.”

Smulders’ Jaap Jansen said: “We see the development and production of the tripod as a perfect extension of our product portfolio and an excellent opportunity to further develop the Wallsend site in the UK.

“The development and production together with Sif is a continuity of utilising our complementary strengths and capabilities in engineering and production of offshore wind foundations.”