In recent years there have been two significant trends in the wind industry: developers seeking higher quality wind resources and turbines growing in size. In response to these developments, the idea of 'floating' offshore wind turbines is becoming increasingly popular. Because they float, these turbines can provide developers with better access to offshore wind resources, unconstrained by water depth. Done right, they include a support structure able to accommodate today's large, and tomorrow's even larger turbines.
Instead of relying on physical foundations like bottom-fixed turbines, floating platforms are attached to the seabed by mooring lines. This means that they can be viably deployed in much deeper water – good news for countries with deepwater coastlines like Norway, Portugal and Greece.
There are three main types of floating wind platforms. One type, known as ‘ballast stabilized,’ uses spar buoy platforms with catenary mooring drag-enabled anchors. A second, called ‘Tension Leg Platforms’ or ‘Mooring Line Stabilized Platforms,’ is attached to the seabed with suction pile anchors. The third type is the ‘Buoyancy Stabilized’ platform, which employs a ‘barge’ type device with catenary mooring lines.
A key advantage of using floating wind platforms is that they allow developers access to previously inaccessible waters where there is stronger yet less turbulent winds – helping to reduce the overall cost of wind energy.
Another benefit is that floating platforms can generally be commissioned and assembled at the quayside, without the need for heavy-lift jackup or dynamic positioning (DP) vessels, further reducing the cost and risk of deployment activities.
“Eliminating offshore lifting operations also provides for decreased weather window restrictions on installation,” says Craig Andrus, Senior VP – Europe at Principle Power.
The fact that foundations are not necessary with floating technology also means that piling activities and sea life disturbance can be minimized - greatly reducing negative environmental impacts. Moreover, reduced geotechnical requirements mean that core sampling is only needed to test the seabed ahead of appropriate anchor selection, as opposed to the necessity of core sampling at every pile site.