LEIDEN, the Netherlands – Heerema Marine Contractors has developed a new technique for installation of floating offshore wind structures.
Current proposals involve assembling floating foundations in port before a wet-tow to the offshore location. According to the company, this brings logistical challenges, and restrictions in terms of the number of suitable harbors.
The new “Floating to Floating” installation method does not require a wet-tow and dispenses with the need for marshalling yards. It allows floaters to be constructed on land before being dry-towed on a transport vessel to the location.
On arrival, Heerema will employ a floating installation frame to lift the floaters from the vessel, and then perform the installation. The frame submerges the floaters down by weight, removing the need for ballasting or tensioning systems and also reducing the duration of the installation.
Bottom foundation work can be executed in parallel through optimizing the capabilities of Heerema’s semi-submersible crane vessels, the company added. The floaters’ volume and weight are said to be reduced through removals of the need for wet-towing. And with the floater being lifted directly from the transportation vessel at the offshore location, both the floater and wind turbine generator can be optimized for in-place conditions.
In addition, the solution enables a “low-tech” floater design through integrating installation needs such as ballasting provisions into re-usable installation tooling, without the imperative to build these functionalities into each floater. According to Heerema, using space onboard transport vessels to deliver multiple floaters directly from the fabrication yard to the offshore wind site transport cuts marshalling costs. And removing the need for in-port assembly of the floater means that less space and draught is required in the port.
Without time-consuming and weather-sensitive wet tows and mooring connections, higher throughput is possible on floating wind projects, the company claimed.
The crane-supported floating to floating installation method is based on proven technologies from the oil and gas floating platform sector, enabling savings of tons of steel per floater and reduced project capex, Heerema concluded.