Floating offshore wind turbines

Wind power is a growing source of renewable energy. There is increasing demand for wind turbine generators offshore, as offshore wind is steadier and stronger than it is on land. Additionally, offshore wind farms have less visual impact on the landscape.

However, the majority current foundations for offshore wind turbines are bottom fixed, meaning they can only be used in areas with suitable water depths and seabed conditions. These foundations require relatively large water depths for inshore assembly or costly heavy lifts for installation offshore.

Floating wind turbines are promising solutions for producing power with a potential for covering deep waters where 80 per cent of wind resources are located. But designing a reliable, durable and cost-effective floating substructure has proven challenging.

Dr.techn.Olav Olsen AS has developed the OO-STAR in response to the need for innovative solutions for offshore floating wind. The IPR are fully owned by the company Floating Wind Solutions AS which was recently acquired 100% by the French company Boygues Travaux Publics.

The OO-STAR is a robust, semi-submersible floating substructure for wind turbines. The unit is capable of supporting heavy turbines even under harsh conditions, and can be positioned in areas that are unsuited for bottom-fixed turbines.

The OO-STAR does not require deep waters for assembly – only a water depth of 10 m. The complete unit can be fully assembled at quayside by land cranes before being towed by standard offshore vessels to site and installed in pre-laid moorings.

The OO-STAR is well suited for modular fabrication, and can be produced worldwide by local contractors. It has great potential for industrialisation through standardisation and mass fabrication. It can be constructed from concrete and/or steel to meet local fabrication requirements, and to optimise cost and durability. However, the concrete option offers great potential for local fabrication and local content also in countries with no steel fabrication yards.

The OO-STAR is scalable for wind turbine generators of well over 15–20 MW, without size limitations related to assembly and installation. The rated power per generator is expected to increase, which will in turn help to reduce the cost per MWh, making offshore wind a more competitive source of renewable energy.

The global offshore wind market is expected to grow from an estimated USD 27 billion in 2017 to some USD 55 billion by 2022.

Founded in 1962, Dr.techn.Olav Olsen is a structural and marine consulting company and one of the world’s leading designers of offshore concrete structures.

The company is part of the Norwegian Offshore Wind Cluster. Along with a group of companies from the cluster, Dr.techn.Olav Olsen in 2020 received funding through the EU’s Horizon 2020 programme for one of the largest EU-funded projects in Norway, the Flagship project for offshore wind in Rogaland, Norway.