|An artist's impression of GE's 12-MW Haliade-X wind turbines. The turbines may only be the biggest machines in the sea for so long as manufacturers scramble to bump up scale.
From a 12-kW experiment in 19th-century Scotland to 12-MW giants that will stand twice as tall as the London Eye, wind turbines have undergone a significant engineering evolution. And as machines become ever-more powerful, outpacing the industry's expectations, project developers and turbine makers — rather than being concerned about the limits to growth — are hungry for even greater scale.
The first wind turbine used to generate power was built by Professor James Blyth at Anderson College in Glasgow in 1887. It was 10 meters high, had a generating capacity of 12 kW and powered a single home.
Fast-forward to 2010, the average offshore turbine was 3 MW and stood at around 100 meters, according to the International Energy Agency. That generating capacity is set to quadruple by 2021, when General Electric Co.'s 12-MW Haliade-X turbines become commercially available. And the IEA expects that by 2030, turbines will be soaring more than 250 meters high, with nameplate capacities of 15 MW to 20 MW.
The industry has underestimated the growth in the size of turbines in the past. "If you look at the development, we had 2.3 MW, basically an onshore turbine that we put offshore," Gunnar Groebler, senior vice president for wind at Vattenfall AB, told S&P Global Market Intelligence last month. "And then somebody said, 'We're going to build 3.6 [MW] or 4 MW,' and people said, 'Come on guys, this is double the capacity, how can you?' And now the 6 [MW] and 4 [MW] are running like a clock."
'We need big machines'
The demand for these new supersize turbines is coming from multiple corners of the industry. As pressure on offshore wind prices squeezes margins, larger turbines offer sought-after scale effects.
Non-technological reasons like planning restrictions are also bolstering the case for bigger machines. There are discussions around distance requirements for U.S. offshore wind farms, for example, aimed at safeguarding the environment for the country's fishing industry.
"For that kind of pattern we need big machines," said industry veteran Henrik Stiesdal, who most recently headed up Siemens Wind Power's technology department until his retirement in 2014.
Will Sheard, global due diligence manager at technical consultancy K2 Management A/S, sees further growth potential for the turbines. But the engineering of the next mega-turbines will require additional scrutiny.
The new Haliade-X turbine represents a significant jump from the 6-MW to the 12-MW model, he said. "That jump in doubling the capacity does cause some concern."
The Haliade-X, currently being tested, boasts blades longer than a soccer field, and according to GE produces 45% more energy than the most powerful turbine currently on the market. GE has already received orders for the machine, including from Equinor ASA and SSE Renewables Ltd. for their 3.6-GW Dogger Bank offshore wind project in the U.K.
Sheard sees the blades as a main factor limiting growth. The size pushes manufacturing to its limits, he said, and achieving the required rigidity could become more challenging with growth. "As blades get longer, they bend more in the wind," he added. In rough conditions, blades that are not sufficiently strong risk hitting the tower.
A solution to the bending blades could be the use of carbon fiber technology, said Stiesdal — a lever the industry has not fully exhausted yet. "I have myself erroneously worried about this for many years. And I was always proven wrong."
Financing the growth
While some developers may prefer not to take the risks that come with deploying a new generation of turbines, in terms of risk aversion, lenders are usually the more concerned stakeholders. "Financiers will request additional warranties" when new turbines are selected for a project, said Jan-Peter Elffers, co-founder of financial advisory boutique Amsterdam Capital Partners BV.
But there is also substantial trust in the turbine manufacturers, especially the legacy names like Siemens Gamesa Renewable Energy SA and Vestas Wind Systems A/S, Elffers said in an interview, and they cannot afford to lose that trust.
If a failure occurs and the manufacturer cannot or will not fix the machine, "that could be the end of their reputation," he added. That can even mean going beyond the repair requirements agreed in the contract.
Elffers, who has advised on a host of offshore wind projects, mostly in the Netherlands, said there is vast appetite from the financial community for new wind projects. "Parties just don't want to miss out on opportunities" to put their money into new deals, he said. When it comes to new turbines produced by the reputable manufacturers, "it has not been an issue to get those turbines financed."
'No visible end in sight'
For Stiesdal, turbines are only set to get ever-more powerful. "There is no visible end in sight" when it comes to scaling the technology and "there is nothing that GE does in their extrapolation that can't be further extrapolated."
The industry does have a reason to be confident in the equipment, as large-scale failures have been few and far between. One incident Stiesdal remembers was the Horns Rev 1 offshore wind farm in Denmark in the early 2000s. The turbines deployed for the project by Elsam Engineering A/S, Vestas Wind Systems A/S and ABB Ltd. had serial defects, affecting the transformer, gearbox and blades, and they were later upgraded and reinstalled.
"I had a lot of concerned people [reaching out] from the finance sector" about the issue, Stiesdal said. Since the upgrade, the wind farm has been operating normally. "We had this huge disaster, but we got over it," he added. Should another incident occur, there will be some recoil. "But we will get over it."