Dogger met-masts ready to go

Fred Olsen Windcarrier’s Brave Tern installation vessel is set to put in the first of two meteorological masts featuring ground-breaking “suction bucket” foundations at the vast £3bn ($4.7bn) Dogger Bank wind development site off the UK’s east coast.

The flask-shaped 165-tonne steel structures, built at Belfast’s Harland and Wolff (H&W) yard using a design from Danish outfit Universal Foundation, are being trialled for developer consortium Forewind as cost-cutting foundations for wind turbines in mid-range water depths.

Based around a squat cylindrical “skirt” that pulls itself down into the seabed using a system of high-pressure pumps so that the soil becomes a structural support to root the tower and turbine in place, the concept – branded the Bucket Foundation – was developed through The Carbon Trust's technology-mentoring Offshore Wind Accelerator (OWA) scheme.

"This is the first deployment of the Bucket Foundation in UK waters," says Phil De Villiers, head of the OWA programme. "We're excited about what this means for offshore wind development. The foundations represent 30% of the total cost of a wind farm. Reducing the capital and installation costs could really make an impact on the viability of future projects."

Installation of the foundations marks the first stage of construction at the Dogger Bank zone 125km off eastern England's coast, where water depths range from 18 to 63 metres.

Forewind project director Lee Clarke says: "The foundations will be the first structure put in place at the Dogger Bank site. It's a sign that this project is really beginning to take shape."

The Forewind consortium – made up of RWE, SSE, Statkraft and Statoil – aims to develop the largest of the Round 3 developments to have 9.6GW of output capacity by 2020. Fully developed, the wind farm could singlehandedly supply 10% of the UK’s power.

The met-masts, being supplied by SeaRoc, are set to be installed “towards the middle of February”.

A third Bucket Foundation is being built at H&W for the SSE/Fluor SeaGreen joint venture for a met-mast to be installed in 43 metres of water at its Firth of Tay zone off eastern Scotland.

Earlier models of the concept, which can fix itself into “80-90% of soil types" according to Universal Foundation, have been used for a Vestas V90 erected off the Danish port of Frederikshavn in 2002 and for a mobile met mast installed at the Horns Rev 2 wind farm in 2009.