RWE installs 100th final foundation at Sofia wind farm

The Sofia wind farm will supply the UK with 1.4GW of electricity and will be about fourth in world rankings when it comes to power generation of the world’s offshore wind farms. 

Nearby Dogger Bank, which has three sub-farms within it, will be the largest once operational, generating 3.6GW. Sofia is RWE’s largest project under construction and should be able to power 1.2 million UK homes.

Sofia’s foundations were installed over a 14-month period in fairly shallow water depths of 20-35 metres by Van Oord’s jack-up vessel Aeolus. The foundations are single monopiles with secondary steel fitted offshore, reducing the steel tonnage needed compared with topping the monopiles with an overlapping, separate transition piece, which is more traditional.

“The vessel underwent a project-specific upgrade to its crane system to achieve a 1,650-tonne lift capacity, enabling it to handle Sofia’s heaviest monopiles,” says RWE. “The precision of the installation is critical, as each of the steel cylinders will form a solid base for the massive 14MW Siemens-Gamesa 252m tall wind turbines.”

Environmental concerns

RWE says half of the turbines are being installed with recyclable blades, which is a major change from the norm, where blades have to be simply buried in landfill when they reach their end of life.

Subsea noise pollution was also reduced with a full-scale bubble curtain noise abatement system deployed around 34 foundations during pile driving operations, RWE says.

Developed by Hydrotechnik Offshore, the technology creates barriers of bubbles when the piling, the repeated hammering of the giant steel cylinders some metres into the seabed, is carried out, which RWE says protects marine species in the area.

Cables some 360km in length will now be buried along the seabed in time for the offshore wind farm to be fully operational by the end of 2026, according to plans.