The €18 million project will be installed in 2020, 10km from the coast at the Marine Energy Test Centre, near Stavanger, southeast Norway. The project site has 200m water depths.
The design comprises a tubular steel base with a suspended keel. The tetrahedral structure will be moored to the seabed by three anchor lines and connected to the electrical grid.
In parallel with the final investment decision, Shell has also acquired a majority stake in the project.
The oil and gas firm increased its share of the project to 66% — with Stiesdal Offshore Technologies reducing its share to 1%. Innogy maintained its 33% commitment it acquired in October 2018.
Siemens Gamesa Renewable Energy will provide the 3.6MW turbine for the full-scale demonstration project, while the foundation structure will be manufacturerd by Danish steel specialist Welcon.
Henrik Stiesdal, CEO of Stiesdal Offshore Technologies, said: "Reaching the final investment decision on the deployment and test of our first full-scale demonstration project is a very important milestone for us.
"The benefits of our partners' experience combined with the competences of our manufacturing partner Welcon will put us on the fast-track for rapid commercialisation."Henrik Stiesdal spoke to Windpower TV at the WindEnergy Hamburg 2018 exhibition about the potential of floating wind power
Dynamic testing of a true-to-scale-model of the concept is underway at the University of Maine in the US — where Stiesdal is a professor — and at the wave tank facility at Force Technology in Denmark.
Shell project manager James Cotter said: "Shell is working to grow our renewable power business and sees great promise in floating wind technologies that could change the face of the offshore wind industry over the next decade.
"We want to help accelerate this change by sharing our offshore expertise with our partners in order to progress innovative solutions such as TetraSpar."
Martin Ferreira, head of offshore investment & asset management at Innogy, said: "We are confident that floating wind is going to be an important growth market in the future. This demonstration project lays the foundation for this by giving us a better understanding of both the technical insights and how the cost of floating wind can be driven down."