Sweco evaluating offshore wind power

Sweco is evaluating a new concept for offshore wind parks that will make it possible to get the turbines into place more quickly and will result in a shorter and loss costly installation phase.

The concept that Sweco is evaluating means
that the wind turbine is positioned on a
concrete gravity base foundation that allows
the turbine to stand upright in the water
with the help of its own weight.

The client, Vestavind Offshore AS, has been granted a permit to develop a wind park with an installed capacity of 70 MW in the sea outside Molde on the west coast of Norway. This is the first permit issued for an offshore wind project in Norway. In connection with this, Sweco has been chosen to evaluate a new concept for offshore wind power as a possible solution for the new facility.

In this concept, the wind turbine is positioned on a concrete gravity base foundation that can be used at a depth of 50 metres and for turbines with an installed capacity of up to 10 MW. The foundation is designed so that the turbine can stand upright in the water with the help of its own weight and therefore does not need to be anchored on the seabed. Another advantage is that the turbine can be transported to the right location through a ballast solution, avoiding the need for a costly offshore crane vessel and significantly simplifying the entire installation process. The goal of Sweco’s report has been to evaluate all aspects related to the technical and structural design, the marine activities and the operational phase.

“This is a project that involves large dimensions,” says Anders Kampesæter, Project Manager at Sweco.

He explains that the concrete foundation has a diameter of around 40 metres and that the entire structure weighs approximately 4,000 tonnes, all of which will be transported in one piece several kilometres out to sea.

“Once there, the structure has to withstand the enormous forces that the turbine is exposed to during many years of winter storms in the North Sea,” adds Anders Kampesæter.

In 2007 Sweco Norway began developing a concept for similar offshore wind turbine foundations. Sweco also has experience of oil and gas installations and has developed several different concrete structures for water depths of between 30 and 60 metres. In recent years Sweco has carried out a number of offshore wind assignments for clients like Statoil in the UK and Lyse Produksjon in Norway.

In the next few months Vestavind Offshore will decide which concept to use for ongoing development of the wind farm.