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Wind of change

A new delivery system for offshore wind farms could reduce installation and construction costs writes Kevin Walsh.

In December last year secretary of state for business enterprise and regulatory reform John Hutton set a target that 33GW of wind power should be generated from offshore wind farms by 2020. The Crown Estate (landowner of the UK seabed) is to announce a third round of leasing options for offshore wind farm construction by June.

Projects resulting from the previous two rounds combined are expected to generate 9GW of wind energy on completion, leaving 24GW of power to be accounted for by round three projects.

With the unprecedented level of expansion necessary for the offshore wind energy sector to help meet the UK's renewable energy obligations, the main concern is whether there are enough resources available to construct so many wind farms in such a short period.

Former chairman of the Offshore Engineering Society, Neil Glover, says that using steel base units to support turbine towers is becoming a problem.

"There is a very high demand and if you look at the supply of large diameter steel piles, there is a shortage there."

Large diameter steel monopiles are most commonly used to found off shore wind turbines, but with the cost of steel becoming ever more exorbitant, engineers are beginning to look for alternatives.

A consortium comprising BMT Group, Gifford, Hunter Associates, Bierrum International, University of Nottingham, E.ON UK and DONG Energy have been working on alternatives to traditional transportation and installation methods for offshore wind turbines.

The team is trialling a system where a bespoke Transport and Installation Barge (TIB) is used to install concrete gravity foundations for wind turbines at depths of up to 35m.

Click here for diagram

The project has the dual purpose of reducing industry reliance on steel monopiles for foundations and eliminating the need for the heavy lift ships and jack-up barges typically used during turbine foundation installation.

In addition the large hydraulic hammers usually needed for piling are no longer required, further reducing equipment and support vessel hire costs.

Michael Starling, principal consultant at BMT Cordah, part of BMT Group explains: "We have had a lot of interest already from Austria and Germany. On the continent they're already thinking on a larger scale in terms of turbine size."

"It's the offshore transport and installation part that we've been focusing on, not just cost but the supply chain.

"A lot of the assets that are used to supply wind farms are in short supply. This project is also trying to develop new assets to expand the supply chain," he continues.

Initial feasibility studies for the Department Business, Enterprise and Regulatory Reform have been completed and the results are promising. However Starling says there is still a long way to go.

"I think the actual de-risking and manufacture of the barge will take 18 months to two years, but that wouldn't be the critical part. The critical part would be the development of an offshore wind turbine project around the technology. These kinds of projects take longer than people would expect to get through to the construction phase."

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