First offshore major corrective maintenance in a floating wind turbine

In recent times, we have learned about several major corrective maintenances (replacement of a main component) that have had to be carried out on some of the pioneering floating wind farms worldwide.

This was the case with Hywind Scotland, which had to tow its 5 SWT-6.0-154s to port, and also with Kincardine, which had to do the same with at least some of its Vestas V164-9.5 MWs.

As you can imagine, these maneuvers are expensive and delicate, as they involve disengaging the wind turbine from the mooring systems and disconnecting the power cables to tow them to port, where the component can be replaced in a controlled environment. The problem is that when the wind turbine is returned to its final position, the reverse process has to be done.

We already mentioned back then, in Windletter #37, that these maneuvers would be different in the future, that these major corrective maintenances would be carried out directly offshore.

Well, that future has arrived.

The Kincardine wind farm has successfully completed the replacement of an electric generator, carried out for the first time on a floating wind turbine offshore. It was done with the help of the company LiftOff, which provided the crane that, once mounted on the nacelle, was able to carry out the component replacement.

These types of cranes, being installed directly on the nacelle, eliminate the problems that occur when using a crane from a vessel. Since both the floating turbine and the ship move differently in the water, it can be difficult to perform repairs accurately. By placing the crane on the turbine, the uncoordinated movement between the turbine and the ship is avoided.

Here is a video of the maneuver carried out in Kincardine:

According to LiftOff, the sequence was as follows:

• Vestas removes the anchor points of the damaged electric generator.
• Using the crane, the generator is lowered to the floating platform (this will not be possible with larger components).
• The OSV (Offshore Service Vessel), with its own crane, picks up the damaged generator and places the new one on the floating platform.
• The new generator is lifted with the crane and installed.

In the process, the most critical aspect is that the OSV can safely hoist and lower the generators onto the floating platform, due to the relative movements we explained earlier. Weather conditions are crucial for this type of maneuver.

This first corrective maintenance is just an initial experience of an emerging technology, but it is clear that solutions involving towing wind turbines to port make little sense for the future when we have floating wind farms at a commercial scale.

And what happens when the component that needs to be replaced is a blade or a part that cannot be stored on the floating platform?

Well, solutions are also being sought for that, such as the case of Solve Wind, the joint venture between Esteyco and Liftra, which is developing these types of solutions.

Sergio Fdez Munguía

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