Solid foundation for offshore turbines

Shortlisted design concepts aim to cut wind-farm construction costs

The Carbon Trust has unveiled seven new offshore wind turbine foundation design concepts and methods for transporting them off Britain’s coast.

The designs were shortlisted by the Carbon Trust from more than 100 participants in its global competition aimed at slashing the costs of construction of offshore wind farms and opening up deeper waters for development.

An Anglo-Franco collaboration of Gifford, BMT Nigel Gee and Freyssinet is behind one of the shortlisted designs.

The team’s design centres on a concrete foundation with a large base that allows the structure to self-stabilise under forces of gravity in water depths up to 45m.

Mark Willbourn, marketing director of BMT Nigel Gee, said BMT developed a concept for a submersible barge that would tow these foundations to the wind-farm site. It would then lower the foundation, which would weigh more than 3,000 tonnes, to the sea bed.

He said: ‘There has been a number of concrete gravity base foundations put in over the years but they have been lifted in by very specialised heavy lift barges in one-off operations.’

He added the BMT barges could deploy these foundations on a mass scale through a ‘quicker, slicker’ production process.

The UK government has set a goal for the installation of approximately 6,000 offshore wind turbines by 2020. The Carbon Trust estimates the current cost of such a project is up to £75bn with deepwater foundations accounting for 20 per cent.

The shortlisted designs were chosen because of their potential to reduce costs of foundations by at least a quarter.

Next year, up to three designs will be taken on to the competition’s second phase — largescale demonstration.