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ANALYSIS: Floating turbines get ready to help wind think deeper

The US Department of Energy’s (DoE) announcement yesterday of $28m in backing for seven ground-breaking offshore wind projects may seem like small beer, but it has the potential to give the nascent floating-turbine technology sector the confidence it needs to leap to commercial maturity.

There are currently only a handful of utility-scale floating concepts undergoing testing off Europe and Japan.

But number crunching by GL Garrad Hassan suggests the economics of floating wind farms are becoming more attractive by the day, with construction of a 500MW development in 50 metres of water potentially costing as little as €0.128/kWh – “if steel prices were lower - and hull costs cut”.

The DoE grants will advance the cause of the two front-running designs – Norwegian energy giant Statoil’s Hywind spar buoy and US start-up Principle Power’s semisubmersible WindFloat – while also giving a significant fillip to the University of Maine’s slow-burning plans for a pilot floating wind farm off the east coast.

The Hywind and WindFloat technologies – both imports from the offshore oil industry and chalk and cheese in appearance – have been girding their loins for build-out as arrays for some time.

Statoil’s, which is based around a steel cylinder ballasted to float like a bottle anchored by a spread of mooring lines, was installed off the island of Karmøy in 2009, and flowed some 7.3GWh generated by its 2.3MW Siemens turbine onto the Norwegian grid in its first year of service.

Principle Power’s – a three-legged triangular pontoon structure that derives much of its stability from being moored partly-submerged in the water – has used a 2MW Vestas V80 to produce well over 3GWh of electricity since deployment in late 2011off Portugal, for the EDP-led WindPlus venture.

The $4m each has received from the DoE is meant to fund the engineering and planning needed for multiple-floater arrays, with a further $47m up for grabs to move the projects to switch-on by 2017.

Though Hywind and WindFloat have been the stars of the floating wind power sector, many are waiting in the wings.

As the wind industry heads slowly but surely for water depths beyond 50 metres, fixed foundations – jackets, tripods and concrete gravity bases – won’t make the grade economically. Floating turbines might.

Semisubs have many admirers, with concepts such as Technip’s vertical axis Vertiwind, Fuji Heavy’s Subaru80, and WindSea’s eponymous unit, all inching forward.

Spars, which need a much deeper draft than semisubs at site, have been somewhat less popular, though Norway’s Sway has been testing a part-scale version of its eponymous unit for several years, and Japan’s Hitachi has fast-tracked a 2MW spar unit into production off the Goto Islands.

The dark horse is the TLP – tension leg platform – concept, which uses ultra-stiff tendons to fix a floating turbine to the seabed.

Another oil industry design – and one that has been studied as a floating wind turbine foundation since at least 2006 in the US by organisations including Massachusetts Institute of Technology and the National Renewable Energy Laboratory – the TLP has gained traction lately in Europe.

Spain’s Iberdrola is testing a model of a 5MW version based around the design, and the UK’s Energy Technologies Institute is understood to be favouring US outfit Glosten’s TLP for a pilot project off England.

As GL Garrad Hassan company supremo Andrew Garrad said of the floating wind sector a few days ago: “It is all to play for”.