That is the verdict of Jens Tommerup, the outgoing head of MHI Vestas, maker of today's highest-rated commercially available offshore turbine at 9.5MW, and Martin Knops, chief technology officer of ZF Wind Power, the manufacturer of that machine's gearbox.
They foresee no insuperable technological obstacles to scaling up today’s hard–ware by more than 50% to a nameplate capacity of 15MW, or of their ability to do it within a few years.
But neither believes that the long-term order book comes close to justifying the required investment in the supply chain and supporting infrastructure.
Higher-rated turbines will require longer (and heavier) blades.
That will mean taller towers to ensure rotor-tip wave clearance, which will have an impact on foundation design, requiring upgraded manufacturing and harbour facilities, as well as bigger vessels.
"We are struggling to make that business case," says Tommerup.
"Who will pay an estimated €300 million for product development?" asks Knops.
The spectre of the stillborn Adwen 8MW offshore turbine, now an €860 million drag on Siemens Gamesa’s balance sheet, is easy to discern in this discussion.
New records for offshore wind installations were set in both Europe and China last year, which is encouraging.
But the 4.3GW added worldwide is nothing like sufficient to drive the investment needed for an upshift to 15MW turbines.
The size and scale of some offshore developments tends to obscure the fact that it is still a very small industry with less operating capacity than Texas.
It has generally been assumed that the ready availability of 13-15MW turbines lay behind some of the recent cost-plunging bids for future offshore wind developments in Europe.
That may be an assumption too far, according to MHI Vestas and ZF.
Last hurrah?
Wind power growth slowed a little in 2017, although the 50GW mark was exceeded for the third consecutive year.
But, in something of a reflection of the consolidation among turbine manufacturers, new build was concentrated in just five markets: China, the US, Germany, India and the UK.
Of those five, only China is expected to maintain its 2017 performance this year. Hitting the 50GW mark for a fourth year running looks unlikely.
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