The emergence of floating offshore wind turbines

03 April 2017

Floating offshore wind projects are in full swing. In Europe alone it is estimated that the potential for floating wind capacity could be over 4,000 GW looking at sites with 60m plus depth. 

The potential benefits presented by this sector enable projects to be built at a greater distance offshore in water, which is deeper than the maximum depth for traditional foundations. 

Out in the deep sea floating turbines promise higher revenue returns through stronger, more consistent wind. Under the right weather conditions vessel day rates, such as heavy lift vessels, could also be dramatically reduced from EUR 150-500,000 to EUR 30-60,000, according to Wind Europe. This is primarily due to major repairs being able to take place at the harbour as the turbines can be towed for major repairs.

With 30 plus platform and integrated turbine concepts being developed globally, the case for increasing investment appetite needs to be built around long term survivability and risk mitigation of the features unique to floating technology.

This new method of deploying old technology but in a new way comes with some risk exposure.

For example, wave action on dynamic cables in floating technology (connecting the turbine to export cables via platforms or spar buoys) can cause greater strain through stretching and compression coupled with added lateral movement in the deep water currents. Whilst intensive fatigue and failure testing is undertaken to mimic the dynamic deep sea environment these cables will experience, this is one of the key long term risk considerations. The long term performance reliability of the dynamic cable for floating wind will be under careful scrutiny, as cable related incidents still make up the majority of offshore wind claims. 

Another key aspect for optimisation is the potential for platforms and therefore turbines to tilt dependent on wave height. This places great importance on the capabilities for control, stability and emergency buoyancy.

Whilst established turbine models could be selected for floating installations, the need to optimise output requires much earlier planning integration between platform and turbine suppliers for the specification to incorporate pitch control and optimisation of blade length based on the expected platform tilt of normal operations. 

As technology changes within nacelles, this can lead to suggestion of prototype, it is the role of a good broker to ensure the widest level of coverage is secured. We believe insurers will ultimately be comfortable with these offshore turbines but careful attention needs to be made to ensure all parties understand both the physical and financial differences between floating and conventional sea bed technology. 

For more information please contact Vanessa Anniss, Renewable Energy team on +44 (0)20 7558 3927 or email vanessa_anniss@jltgroup.com

contact Vanessa Anniss
Renewable Energy Partner, JLT Specialty vanessa_anniss@jltgroup.com