Catching the wind: design review

Architectural Review, The, Nov, 2003 by Catherine Slessor

As wind power evolves into a more widely acceptable source of green energy, so more attention is being paid to the form of the wind masts, which tend to be dominant presences in the landscape and often the source of unfavourable public reaction. There is also an inherent contradiction between the aim of producing green energy through wind power, and the often huge quantity of material used for the construction of masts and their foundations. Typically, these consist of a large and heavy tubular steel structure resting on a thick concrete slab supported by massive in-situ concrete piles.

Some time ago, Belgian architects and engineers Samyn & Partners were appointed by Groupe Fabricom, a leading Belgian company involved in the electromechanical industry, to develop a prototype for a lighter and more ecologically conscious wind power mast. Instead of using heavy foundations. Samyn's lightweight version is braced by a network of tensile cables. Three pairs of studded cables are moored just under the propeller and arranged in a 120 degree star-like configuration in plan. The cables splay out at a 45 degree angle linking the shaft to the studs and then run vertically to the ground. A more complex cable configuration increases torsional stiffness for structures in offshore locations. In both cases, three additional cables link diagonally, and in vertical planes, the connecting points of the studs with the mast penetration point in the ground.

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This form has many advantages over more conventional designs. Apart from being a lighter structure (Samyn estimates that the weight of a 100m high mast will be halved), the cables can be used to raise the mast vertically, so eliminating the need for heavy hoisting equipment and allowing generators to be installed in remote locations. It also reduces the size of the foundations, requiring only smaller prefabricated prestressed concrete piles which can be easily removed and have less long-term impact on the environment. At ground level, cables are anchored by concrete discs made up of radial segments buried underground weighed down by soil.

At present the patent for the system is pending and it may be taken up by the Italian national electricity supplier ENEL for two wind farms in southern Italy. Given the abundant nature of wind as a potential energy source, it must surely be only a matter of time before it is exploited on a more intensive scale all over Europe and wind masts become as commonplace sights in the landscape as electricity pylons.

Architect

Samyn and Partners, Brussels

Photographs

Courtesy of the architects

This prototype for a new form of wind mast makes elegantly economical use of materials.

WIND POWER MAST PROTOTYPE