Veja Mate is a deity in Latvian mythology whose name translates to “Mother of the Wind” what might be considered a very appropriate name for the 402MW offshore wind farm being built some 100km off the coast in the German sector of the North Sea.
The foundation installation at the Veja Mate site involved using the largest-ever hydrohammer and the world’s largest jack-up vessel fitted with a 1,500-tonne crane to install the largest monopiles produced so far. “The Veja Mate offshore wind farm was a massive project in every sense and one which has entered the record books,” Taco Terpstra , Senior Project Manager at Boskalis, is quoted as saying in the company’s latest magazine edition.
Boskalis was in charge of the design, procurement, manufacture, transport and installation of the foundations, including scour protection.
The last foundation was installed at the end of the last month and the erection of Siemens 6MW turbines is scheduled to start at the beginning of next year. The wind farm is expected to generate first electricity in the fall of 2017.
Installing XXL monopiles
The XXL monopiles have a diameter of almost 8m, they are up to 85m long and weigh 1,300t. Seajacks Scylla started installing the monopiles in April, while Seajacks Zaratan took care of the transition pieces.
Terpstra detailed on the installation process: “For this operation, we chartered the new jack-up vessel Scylla fitted with a Boskalis pile gripper frame – a structure that was designed specifically for this project.”
“The heavy crane on board the vessel used the pile gripper frame, which was attached to the side of the Scylla and was fitted with two large ring structures, to lift the monopile. The two rings close around the pile. Then the guides on the inside of the rings maneuver the monopile into the correct position and allow it to sink slowly to the seabed.”
“The next step is to secure the pile in the seabed, which takes just a few blows of the enormous hydrohammer. The rings around the frame are then opened and the monopile is driven around 40 meters into the seabed.”
It takes roughly two days to install a monopile, Boskalis said, and every effort was made to minimize the sound of piling, which was limited to 160 decibels.
“But for sure one of the biggest challenges we faced was arranging the seamless coordination of the various production and transport processes,” Taco Terpstra explained.
The Scylla and the Zaratan were operating simultaneously, along with numerous other vessels that were required to transport the materials from Rostock, Aalborg and Eemshaven. Terpstra said: “There were 55 colleagues working full-time on the project at HQ and at the production sites. But during the peak summer period, several hundred people were working on this very special project!”
When fully operational in 2018, the farm will produce over 1.6 TWh of electricity annually for 400,000 households in Germany.
Offshore WIND Staff; Source: Boskalis