Off-Shore Wind Turbine Suction Bucket Support Structure

The Danish company Universal Foundation has developed a gigantic steel suction bucket which will act as a support structure for off-shore wind turbines. It has been engineered to sink rapidly into the sandy sea floor. Once in place, it will become stuck fast and form a rock-solid foundation for a wind turbine above the waves.

The structure works by creating quicksand around the rim of the 16-metre-diameter bucket, so it slips easily into the seabed. When the inverted steel bucket reaches the bottom, a pipe running up through the stem above sucks water out of the bucket. This causes water to flow into the bucket through the sediment, creating a sloppy quicksand at the rim. But when the bucket is in place, the pump is turned off, forming an extremely strong foundation. Trying to pull it out creates a vacuum in the bucket, like when you try to pull your foot out of wet sand on the beach.

Conventional foundations for offshore wind turbines are either a giant steel rod, driven into the seabed, or a steel jacket resembling an electricity pylon. Both need more steel – an expensive material – bigger, more specialised ships for deployment and are more prone to costly weather delays.

Two of the foundations left the Harland and Wolff shipyard in Belfast in January 2013 and will become the first deepwater deployment of the technology once planted 25 metres below the surface at Dogger Bank.

If all goes well, the technology may provide a secure basis for the thousands of giant offshore wind turbines planned for UK waters. The benefits include:

• It can be installed faster and at lower costs than conventional foundations
• It could save developers more than £5bn if used for the 6,000 turbines planned in the next decade or so, because it is 20% cheaper than conventional foundations, which make up about 30% of the cost.

For more details, see the following websites. The Guardian website has good videos, graphics and pictures:

• http://www.guardian.co.uk/environment/2013/jan/22/suction-bucket-offshore-wind?intcmp=122 
• http://www.universalfoundation.dk/
• http://www.harland-wolff.com/Services/Design-and-build-offshore-foundations/Universal-Foundation.aspx