The TetraSpar Demonstrator

The TetraSpar Demonstration Project is the world’s first full-scale demonstration of an industrialized offshore foundation. The project is carried out in a partnership between RWE, TEPCO Renewable Power, and Stiesdal Offshore.

Industrialization in action

Experience industrialization in action in this short film documenting the pioneering TetraSpar floating wind foundation.

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Tetrahedral steel structure

The TetraSpar foundation is a tetrahedral structure made from tubular steel components. The simple geometry enables lean manufacturing, assembly and installation processes and low material cost.

Welding-free assembly

The foundation and keel were assembled without welding at the Port of Grenaa in Denmark, demonstrating a streamlined and industrially scalable assembly process.

Turbine integration

A 3.6 MW wind turbine from Siemens Gamesa Renewable Energy was mounted on the foundation following launch in the harbor basin.

Offshore operation

In July 2021, the complete structure was towed to the Marine Energy Test Centre off Karmøy, Norway, where it was commissioned and is operating at a water depth of 200 meters.

TetraSpar Demonstrator performance

TetraSpar Demonstrator
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The TetraSpar story in images

The TetraSpar foundation components were manufactured at the facilities of the Danish wind turbine tower manufacturer Welcon and transported to the port of Grenaa over the summer 2020. Assembly took place in October and November 2020.

The demonstration project uses the Tetra floating foundation technology in a spar configuration, suited for 100-1000+ meter water depth.

The port of Grenaa in Denmark was chosen as the construction site for the TetraSpar foundation. A flat area at quayside was reserved for the assembly, no special facilities needed. Photo: Grenaa Havn.

The components for the Tetra foundation were manufactured by Welcon A/S in Give, Denmark. Welcon is the world’s leading supplier of offshore wind turbine towers, and its automated production lines are ideally suited for the manufacturing of the tubular braces and tanks for the Tetra concept.

Component manufaturing, at Welcon, center column. The fact that all parts of the foundation were manufactured offsite with industrialized processes makes TetraSpar the world’s first fully industrialized offshore wind foundation – reducing manufacturing hours by 85-90%.

Road transport, center column.

Up-ending of the center column at the port of Grenaa, Denmark.

The assembly involved no welding or other special processes. Key elements of the assembly process took less time than previously expected.

Mounting of the diagonals using maintenance-free proprietary technologies for fast assembly.

Completed foundation and keel.

Transport from the adjacent assembly spot to a submersible barge using SPMTs (self-propelled modular transporters).

Loading the foundation onto the submersible barge.

The barge during submerging.

The barge is fully submerged and the foundation floats in the harbor basin.

Loading of the keel onto the submersible barge with SMTPs.

The barge and keel during submerging.

Installation of the turbine using a land-based crane. Here, the tower bottom section is mounted.

Early morning rotor lifting.

Turbine installation done!

Tow out from the Port of Grenaa on July 11, 2021. The keel is in place under the foundation. Port basin water depth: 10,5 meters.

Underway from Grenaa in Denmark to the METCentre test site in Norway – a towing route of 360 nautical miles.

Towing with keel fully deployed. The keel was lowered once the vessel reached sufficient water depth north of Skagen.

The TetraSpar Demonstrator, moored at the test site in Norway with three anchor lines at 200 meters water depth.

The subsea cable connection to the Norwegian grid was carried out by Bourbon Subsea Services.

The floater seen from the shore of Karmøy at 10 kilometers distance (heavily cropped tele lens photo).

Commissioning was completed November 29 2021 and the TetraSpar Demonstrator has since been in full automatic operation.

Photo credit: The TetraSpar Demonstrator Project ApS.