Floating the idea of a platform for turbines

Sweden’s Hexicon has developed a new solution for offshore wind — a floating platform that can accommodate six or seven large turbines with a total capacity of 25–40 megawatts (MW).

The turbines will be operated and controlled from a hub in the centre of the platform. The installation will be anchored to the seabed but turn on its own axis — allowing it to turn into the wind for the best performance.

The concept has important advantages for offshore wind, says Percy Sundquist, business development manager at Hexicon, part of the Fagerdala group.

Sundquist says: “We are sure we can construct a platform like this at the same cost per installed MW as at offshore wind farms now being built at 20–30 metres’ depth in the North Sea.”

The gap between turbines will be sufficient to avoid turbulence from one affecting the others.

Hexicon has several advantages over traditional offshore wind farm designs, says Sundquist. These include:

lower maintenance costs, because turbines are more easily accessible and platforms can be combined;

the platform can operate for 50–60 years, with the turbines replaced as more efficient models become available;

the platform can be built onshore and then towed out to sea, or assembled on location; and

it is not dependent on shallow waters, and can also accommodate wave-power installations.

“We see a potential in the US, Europe and Asia, and also in the developing world,” Sundquist continues. “Many cities around the world can get a substantial portion of their electricity from a 30MW platform without massive investment in the onshore grid.”

He adds that the concept will undergo a cradle-to-grave life-cycle assessment in co-operation with the Swedish Environmental Research Institute during 2010, and he hopes construction of the first pilot platform can start by mid-2011.

Sundquist estimates that the first platform will most likely be about 60% of the full size — depending on interest from potential partners and customers.

Asbjørn Strand, offshore wind technology and innovative concepts manager at the Norwegian Centre for Offshore Wind Energy, says Hexicon design is interesting, but the crucial question is whether the construction costs can be competitive and the structure solid enough for tough deep-sea weather conditions.