By Ariana Hurtado, Editor and Director of Special Reports
Equinor has been constructing what it says is the world’s largest floating offshore wind farm in the Norwegian North Sea to reduce its offshore operations' CO2 emissions.
Steel cutting started on the Hywind Tampen wind farm at Kværner’s yard in Stord, western Norway, in late 2020, and the wind farm should become fully operational in 2023.
In November 2022, Equinor reported that seven of the 11 turbines were expected to start operating in late 2022, with the other four to be assembled this year during a suitable weather window. But even with seven onstream, Hywind Tampen will be the world’s largest operational floating wind farm, Equinor said, with a capacity of 60 MW.
The new power arrangement should cut the fields’ CO2 emissions by about 200,000 metric tons annually, the company added.
Hywind Tampen, with a full system capacity of 88 MW, is 140 km offshore in the Tampen area in water depths ranging from 260 m to 300 m. The turbines have been installed on floating concrete structures with a joint mooring system.
"This project would be a significant step forward for the energy transition on its own – taken together, Hywind Tampen and Equinor’s earlier Hywind Scotland pilot project will generate around half of the world’s floating wind power," Mammoet stated in a press release about the floating wind farm. "The market is still developing, and although various component designs, installation techniques and deployment methods are being considered and prototyped, none have been commercialized at full scale. Floating foundations were required for this project as the water depth and seabed geology in the Tampen area made it impossible to install conventional fixed-bottom turbines."
View the Mammoet photo gallery above to see assorted images of the Hywind Tampen project.
Assembly challenges
Mammoet, a heavy-lift and transport specialist, said the main challenge was the assembling of the entire 8.6 MW turbines—including tower sections, nacelles and blades—onto huge 107-m spar buoys that lie mainly underwater. According to the company, this needed to be performed in the controlled environment of a port where the whole system could be kept as static as possible before the completed turbines were towed out to their installation site.
With such huge floating foundations, this port required an exceptionally large draft, ruling out jackup vessels, which would be too short to assemble the turbine sections. Also, though conditions at Gulen Industrial Harbor were calm, using crane vessels would increase the complexity of assembly engineering, which would then require transfer between two floating objects. This could, in turn, delay the integration phase and lengthen the offshore installation campaign, increasing project costs, Mammoet said.
A spacer barge between the quay and spar foundation was needed to ensure adequate clearance between the base of the foundation and the seabed. Turbine components would therefore need to be lifted over the quay edge, over the spacer barge, then onto the foundations themselves: a distance of about 143 m.
Following its experience during the deployment of the world’s first floating wind farm, Hywind Scotland (also operated by Equinor), Mammoet was engaged to undertake turbine assembly and associated port handling work.
Martin Tieman, Mammoet project manager, explained, “We recognized that we would need a crane with a huge outreach to make the required lifts. The majority of land-based cranes in any fleet would not be able to achieve a 143-m distance at these weights, but we knew that if it could be done the project would benefit significantly. This would create a smooth production line from marshalling yard to turbine assembly to commissioning, all at the same location, optimizing the use of offshore assets.
"This led us to look at the use of our PTC 200-DS crane, which is proving to be in high demand for big offshore wind projects such as the Greater Changhua development in Taiwan and Seagreen Offshore Wind Farm in Scotland. With the port confirming the quayside would be able to provide the required ground bearing pressures, we were able to put together a plan that would deliver a comprehensive package of port handling and assembly of all eleven turbines of Equinor’s development.”
View the Mammoet photo gallery above to see assorted images of the Hywind Tampen project.
Overcoming severe weather
Although large ring cranes are built to withstand strong gusts, components such as these (with a large surface area designed specifically to catch the wind) are another matter. To counteract this, the PTC 200-DS was modified to ensure precise control of components even when winds were strong, meaning that there would be fewer potential stoppages due to the weather and the turbines could be completed sooner, Mammoet said.
These modifications allowed the crane to work with third-party blade yoke and tugger winch systems, which orient the load under hook without the need for taglines operated by hand. This prevents damage to relatively delicate turbine blades and increases levels of safety on site.
Besides lifting, strong port handling capabilities were required to receive tower pieces, nacelles and blades from vessels and store them so they could be retrieved quickly, maximizing utilization. Mammoet managed this scope, assuring the main lifting asset was in use for as much time as possible.
Alongside the PTC 200-DS, 24 axle lines of SPMT and a range of smaller cranes were used to handle the movement of components; as well as an LR1750 crane to assist the PTC during lifts that required rotation of components. This further helped to keep idle time as low as possible for all assets, minimizing handling maneuvers overall.
ESG
During summer 2022, Equinor announced that a bird radar is monitoring bird behavior in the Hywind Tampen area. The first turbine was installed offshore in May 2022, and the radar from Robin Radar Systems was set up on one of the 11 turbines. The bird radar is part of a larger study to investigate how bird life is affected by offshore wind.
