None of the existing wind turbine installation vessels can install next-generation 15+ MW turbines, stated IHS Markit in a recent report. This is incorrect, says Heerema Marine Contractors’ CEO Koos-Jan van Brouwershaven. ‘Our vessels Thialf and Sleipnir are already suitable to install these 15 MW turbines while floating on DP. At present, we are developing and finetuning the supporting tooling for these operations. With some adjustments to the crane boom, it is even possible to install 20 MW turbines.’
Thialf and Sleipnir are semi-submersible crane vessels. With Sleipnir’s cranes even capable of lifting structures up to 195 meters above sea level. In addition to installing foundations, moorings, and structures in deep water, the vessels can also be utilized to install the largest and heaviest wind turbine components.
Installing turbines with a floating vessel
‘We currently have a project in the Baltic Sea, where we are going to install the 9.5 MW turbines for Arcadis Ost. It will be the first time this will be performed with a floating vessel for an offshore wind farm of this scale,’ says Heerema’s Director Wind Koen van der Perk.
In 2019, Heerema announced it was working on the new installation method for Arcadis Ost. This floating installation method provides two unique advantages: it avoids all interaction with the soil, thereby reducing the project’s risk compared to a traditional jack-up installation, and it allows for a reduced installation time. It is based on utilizing a floating installation vessel to assemble the wind turbine generator (WTG) components. The vessel will have all turbine components on its deck, including a dummy tower. This tower will provide a stable platform onboard the vessel to assemble the nacelle and the blades.
The first step will be lifting the WTG tower onto the pre-installed turbine foundation. The second step is the most advanced element in the assembly process which includes lifting the nacelle onto the dummy tower and attaching the blades. This process ensures full control over the blades, thereby guaranteeing a safe and highly reliable blade assembly. After assembling the rotor nacelle assembly (RNA) on the installation vessel, the complete RNA will be lifted as one piece onto the WTG tower.
Van der Perk adds: ‘We are now working with developers and turbine suppliers to advance this technique for larger turbines, over 15 MW, without having to modify our vessels materially.’
Solution on the market this year
Heerema aims to obtain the approvals for installing 15+ MW turbines using its dynamically positioned, floating vessels this year, and will then enter the market.
‘It is always good for the world to know that there are other options,’ Van der Perk concludes. ‘Sometimes we do things a little under the radar until we are sure that something is really going to work, and we certainly have that belief now. After we obtain all final approvals, we will offer our solution commercially before the end of the year, which allows us to carry out projects from 2024 onwards.’