Supporting innovations in floating offshore wind

The floating offshore wind sector’s worldwide capacity accounts for a total of about 100 MW. While that doesn’t yet measure up to the 35 GW of its fixed offshore wind forebearers, its current project pipeline totals an impressive 20 GW to be installed by 2030. 

Which floater design to use?

Four projects based in France are now in the final design phase, located in different marine environments. They utilize varied floater concepts based on four main foundation types, each with a unique set of advantages and drawbacks that must be assessed and matched to the specific installation environment:

• Featuring a relatively shallow draft, semi-submersible foundations are flexible for different site conditions. However, their high steel mass and many welded connections make them heavy and complex to manufacture.
• Spars are well-proven, ballast-stabilized structures with a large draft that provides high inertial resistance to pitch and roll motions. The large draft can be a challenge, though, for both assembly and operational sites, as well as transportation routes.
• The low structural weight of the substructure of a tension-leg platform (TLP) makes it a cost-saving option. But the risk of mooring failure presents high operational risks and adds constraints in relation to onsite soil condition.
• Barge foundations offer the shallowest draft of all, facilitating turbine installation alongside a quay. They are more affected by wave-induced motions, however, requiring more robust mooring systems.

Identifying new challenges

Oil and gas (O&G) industry players aim to leverage their expertise in offshore design and installation, drawing on some similarities between the sectors. However, the O&G platform environment is different from the shallower waters of floating offshore wind projects. Synthetic mooring lines don’t face the same amount of sunlight and particle ingress when used in the deep waters of O&G platforms that they will in the shallow waters of floating offshore wind territories. These materials thus need to be tested and qualified for such applications. 

As floating wind projects reach the commercial stage, high-voltage dynamic cables are another potential challenge that could affect them. To mitigate the risk of degradation, cables must be tested from the design stage, and fabrication and installation should be closely monitored. Bureau Veritas is partnering with leading international cable manufacturer Nexans to establish minimum standards for cable manufacturing. This will raise awareness of the importance of carefully selecting cable manufacturers and cable-laying operators to reduce risks and ensure full operational functioning from the start.

Safely steering the floating offshore wind industry

Over the last 10 years, Bureau Veritas has worked closely with floater designers, helping them with derisking and enabling their technologies’ go-to-market. This is primarily done by performing Qualification of New Technologies and issuing Approvals in Principle for all main types of floaters and materials (steel, concrete, composite) in use.

Bureau Veritas is also working on all four floating offshore wind projects currently under development in France, helping clients assess their project designs and fabrication/installation procedures. And in an atmosphere where regulatory frameworks don’t yet fully exist, Bureau Veritas is developing guidelines such as NI631, NI572, and NI525, which address both classification and certification of floating wind turbines. 

Floating offshore wind is still in its infancy, but it is developing quickly. Risk-based inspection of design and materials from the earliest stages will prove key to the industry’s future success.