Offshore wind turbine foundations in extreme environment

Published: 16-02-2016

How do you design foundations for offshore wind turbines to withstand earthquakes as well as typhoons - and be produced under local, Taiwanese conditions?

Imagine a wind turbine where the blades sweep an area equivalent to nearly two football fields, and the blade tip almost reaches the height of the Great Belt Bridge pylons. Now imagine that the wind turbine is erected at water depths of twenty meters.

Obviously, this requires a robust foundation, but the challenges continue: The foundation and turbine must be able to withstand huge waves and typhoons with wind speeds over 200km per hour. In addition, the frequent earthquakes threaten to transform the sandy and soft seabed to a bottomless pit with a carrying capacity of next to nothing.

Oh, and then there is an issue with the torrential rain. Heavy rain transports sand from the mountains into the sea, and this constantly changes the seabed, where the foundations are to be erected.

The above is a pretty good description of the conditions for designing the foundations for an offshore wind farm in the Taiwan strait, which is a project NIRAS has recently won.

Valuable knowledge for future projects

"This is quite a challenge. Substantial elements in this project have never been developed before, so we are in for learning a few lessons. However, we see it as a good investment, because we end up with valuable knowledge for future offshore wind projects," says Project and Market Director Claus Gormsen, who has worked with offshore wind projects for more than 20 years.

In 2014 NIRAS was elected as client consultant on the same project. When the developer realized the difficulty of designing the foundations, this assignment was also handed to NIRAS.

READ MORE: NIRAS wins offshore wind project in Taiwan

The project is divided into a pilot project with two jacket structures and a main project with the remaining 28 jacket constructions. All 30 must be installed before the end of 2016, and because of the weather conditions, the schedule is even tighter:

Downside to the favourable wind conditions

"The downside to the very favourable wind conditions at the site is that the size of the waves makes it impossible to install anything from October to April. That also contributes to making the installation of foundations, cables and turbines a major challenge," says Claus Gormsen.

Finally, Claus Gormsen points to yet another challenge in the project, which very well may prove to be the greatest of them all:

"Taiwan has no experience in manufacturing and installing this type of offshore structures. Therefore we need to design the jacket structures in a way so they can be constructed and erected with the available equipment and expertise. Therefore we need to be particular scrupulous with our control, because it takes completely different skills to weld offshore installations than just putting two iron girders together into a house," says Claus Gormsen.

Contact info

Claus Gormsen Market and Project DirectorAllerødT: +45 4810 4284E: Send E-mail
Tim NormanManaging DirectorCambridgeT: +44 1223 803750E: Send E-mail
Further contact info
© NIRAS Consulting Ltd. - St Giles Court, 24 Castle Street. Cambridge. CB3 0AJ UK. - T: +44 (0)1223 803750 - E: - Sitemap

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