TetraSpar Demonstrator

TetraSpar Demonstrator is a single‑unit full‑scale demonstration of Stiesdal’s modular tetrahedral floating foundation deployed at the METCentre test site off Karmøy, Norway. The demonstrator carries a 3.6 MW Siemens Gamesa turbine and was assembled in Grenaa, Denmark using an industrialised, welding‑free modular process before being towed to site and commissioned in late 2021. The project was developed by a consortium (Stiesdal Offshore, Shell, RWE and TEPCO Renewable Power) to validate rapid factory manufacture, simple quayside assembly and cost‑efficient deployment of a spar‑type floater that can be handled from ordinary, shallow‑water ports. Key technical firsts included the tetrahedral steel space‑frame with a suspended keel (deployed ~50 m below the floater), modular pinned connections, and a tow‑and‑install sequence that avoided specialist deep‑water port facilities. During its operational phase the demonstrator delivered strong performance metrics (high availability and an aggregate capacity factor in the order of 50–63% in different reporting periods, and roughly 70 GWh cumulative energy reported), providing continuous operational data for certification and design iteration. Cable and offshore installation scope was handled by industry contractors (including Bourbon Subsea Services for installation activities) and the unit exported power to shore via the Unitech Zefyros connection. Following several years of successful operation the consortium appointed Global Maritime / onshore partner Semco Maritime for decommissioning works in 2026, timed to allow full subsea inspection and material verification that will inform the commercial TetraSub designs.