Q OFFSHORE STRUCTURES
THE ARTICULATED WIND COLUMN
With 40 years’ experience in offshore
structure management, IMarEST fellow Peter Broughton has now developed a wind turbine loading column with a base that rotates about both horizontal axes
22 Words: Peter Broughton T The proposed Articulated Wind Column
he development of offshore wind as a source of energy is being pursued in many countries throughout the world. In UK waters the development of offshore wind has been restricted to
relatively shallow water locations, with many of the planned sites being a considerable distance from shore resulting in high electrical transmission costs. The development of ‘floating’ or ‘compliant’ sub-structures, such as the Articulated Wind Column, allows development of deep water sites which are closer to shore. This structure can be adopted over large
areas of the offshore UK and the continental shelves around the Republic of Ireland, France, Spain, Japan, Taiwan and the USA. With the capability to accommodate the
largest turbines of any configuration and the optimisation/minimisation of power transmission cable lengths, together with the introduction of modern methods of mass/ multiple fabrication of the substructure, this allows economic development of future offshore wind fields to be competitive with other methods/forms of electricity generation.
The Articulated Wind Column (AWC) – a
project developed by Marine Engineering Energy Solutions Ltd and Doris Engineering/ ODE – has been designed to support an 8-9.5MW turbine located in 90m of water. The structure essentially consists of two main elements – the compliant vertical column, and the base which is located on the seabed. For simplicity of design and fabrication the
two main elements of the AWC structure are fabricated in reinforced concrete, although steel fabrication of both elements is possible.
The two main parts are connected
together through an articulated joint, which allows rotation about both horizontal axes. The two main elements would be constructed separately, but joined together prior to marine transport and installation. The performance of the compliant column
in being able to achieve near verticality is through the natural buoyancy of the column. Because of the articulation between the column and base, the column and base design allows for any possible out of level of the seabed. The stability of the base unit on the seabed is achieved with the placement of heavy iron ore ballast offshore. The technology for the AWC is based on
that developed for offshore oil loading columns, such as the Maureen Loading Column, which was placed in 93m of water in 1982. Various forms of the column and base structures have been considered. These are referred to in two patents for Europe and the US.
The Maureen Loading Column with a tanker hawser provided a maximum 210 tonnes of load – comparable to the extreme design load of a large offshore wind turbine
Offshore potential Opportunities exist in many locations around the world. These include many locations around the UK, around Southern Ireland, offshore France, and many locations offshore
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