A multi-disciplined team in the UK which includes Gifford, Hunter Associates, Bierrum International, the University of Nottingham, EON UK, DONG Energy, BMT Nigel Gee and BMT Cordah is designing a method of transporting and installing 'concrete gravity foundations' that can be placed on the seabed at depths of 25m and beyond, enabling a much larger area to be allocated for offshore wind farms.

The Government-funded project has developed a new, concrete design for the turbine tower with a large base allowing the structure to be positioned on the seabed and self stabilise under forces of gravity.

The development team is also devising a transportation and installation system for the large offshore structures, typically weighing over 2,000 tons, whereby the concrete towers are attached to submersible barges and towed out to position and settled into place. The major obstacle to deepwater installation is the practicality of handling large concrete structures and having the vessels from which to do so.

The aim of the project is to achieve substantial reductions in both the construction and installation costs of deep water wind farms. The team involved hopes to reduce cost compared to the current steel monopile/tower solution. This would be particularly valuable for larger turbines in deeper water such as in Round 3 of UK licensing and at more challenging sites such as Scarweather Sands and the German North Sea.

The developing solution is based on the use of conventional offshore construction methods together with relatively inexpensive dedicated barges and conventional offshore support vessels for the transport and installation of foundations. This would minimise the land area required for construction and the expense of specialist vessels whilst maximising the use of existing vessels.

The project has received funding from the UK Technology Strategy Board under their Emerging Energy Technologies programme and from EON UK.

The concrete gravity foundations would be constructed on shore then transferred to the seabed (in harbour) using a submersible launch platform. A transport and installation barge is then towed to the foundation, where it is flooded until it rests on the foundation and can be connected to it. Water is then pumped out of the barge, lifting the foundation from the seabed for towage to the wind farm site. The barge is then flooded again until the foundation rests on the seabed. The foundation is then disconnected and the barge refloated to be towed back and pick up the next foundation.