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Floating wind power plays the generation game

ANALYSIS | New-look designs now emerging could supercharge the fast-growing sector into the energy mainstream, writes Darius Snieckus

Even by the precocious standards of the fast-maturing floating wind power sector the last fortnight has been an extraordinary one, as no fewer than four next-generation designs made meaningful progress towards commercialisation.

Two Spanish floating wind technology outfits, X1 Wind and Saitec, between them pulled in almost €6m ($6.8m) in European Union funding to advance their concepts, known respectively as PivotBuoy and SATH (Swing Around Twin Hull) in part-scale versions, each company with an eye on a 10MW+ model in the next few years.

The prototype of the PivotBuoy, which will be topped with an adapted 225kW Vestas turbine, combines a jointed-steel tension leg platform and so-called single point mooring (SPM) system in a downwind design that ‘weathervanes’ with the prevailing wind, to better capture the resource. The SATH, though it also weathervanes on an SPM, is a different animal, based on a joined pair of cylindrical pre-stressed concrete hulls.

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The two designs will both be installed off the Canary Islands next year, in waters not far from the installation site of EnerOcean’s part-scale W2Power prototype – the world’s first twin-rotored floating wind power platform – which is about to sail out of a construction yard on Gran Canaria.

The long-gestating technology – a weathervaning triangular steel semisubmersible with angled towers flying turbines at two corners – will be put through its paces in a fast-track testing programme at 1:6 scale flying 100kW turbines, as the developer ramps up plans for a maiden array of full-size units.

In Sweden, SeaTwirl set the seal on a €6.7m investment from Belgium’s Colruyt Group and Norway’s Norsea to finance development and installation of the company’s flagship 1MW S2 unit – a vertical-axis-rotored concept with seawater-based storage system – which is slated to be moored in the North Sea next year.

"A forecast is just that. We shouldn't let it hold us back from a much bigger build-out of floating wind by 2030."
Henrik Stiesdal

The first wave of utility-scale floating wind – the various projects of 300MW to more than 1GW taking shape for development in the US Pacific, through Europe’s northern and southern seas, and in markets in Asia including Japan and Korea – is expected to dominated by the first movers in the sector – Equinor, Principle Power and Ideol, which all have technologies tested at full-scale and international order pipelines.

But floating wind's success will hinge on its industrialisation in key regional markets, as full-scale projects test the sector’s ability to cut levelised cost of energy to match levels now anticipated for conventional, bottom-fixed offshore wind, of sub-€50/MWh – that’s a far cry from the €240/MWh the French government is underwriting to get four flagship arrays into operation off its Atlantic and Mediterreanean coasts.

The cost curve is dropping sharply already. Equinor carved 75% out of the cost of its Hywind spar concept by moving it from prototype to array and it expects to halve the figure again with its next iteration of the model. Other front-runners are seeing similar capital reductions as they push ahead with streamlining the engineering and economics of their platforms.

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But the new designs now emerging onto the seascape are approaching floating wind power from a different tack.

The start-ups behind them have started from the first principles of mass production and mass installation — where the early spar, semisubermisble and tension leg platform concepts have been adapted from the ‘one-at-a-time’ needs that shaped floating offshore oil & gas platform designs — and have woven in rethought weathervaning-centred mooring technologies to help these units harness wind-streams more efficiently.

If they get it all right – and full-size models of these next-generation concepts are being sped toward commercial-readiness – then these aspirants could quickly make analyst forecasts pointing to a global floating wind fleet as large as 15GW by 2030 look decidedly underambitious.

As Henrik Stiesdal, who is developing another new-look, industrialisation-minded design, the TetraSpar, with Shell and Innogy, remarked recently: “At a point, a forecast is just that. Maybe is it good to motivate [the sector] right now, but we certainly shouldn't let it hold us back from achieving a much bigger [build-out of floating wind farms] around the world by then.”

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