The race to build the world’s largest wind turbine
Size does matter.
Back in March 2018, General Electric (GE) grandly unveiled the world’s most powerful offshore wind turbine named Haliade-X with a 12 megawatts (MW) generator rating. It was said that the turbine, with 107-meter-long blades and a 220-meter-long rotor diameter (the diameter of the swept area of a turbine), produced 45% more energy than any other offshore turbine available in the market. The company held its head up high for over a year until May 2020, when Siemens Gamesa launched the new SG 14–222 DD offshore wind turbine. With production scheduled to begin in 2024, it was the largest wind turbine ever publicly announced with a nominal power output of 14 MW, that can be increased to 15 MW by a “Power Boost” function, and a rotor diameter of 222m. The turbine put Siemens Gamesa ahead in the race, but again the lead was short-lived as Vestas announced in February this year that it will introduce the V236–15.0 MW turbine, with 115.5m blades and 236m rotor diameter. The first prototype installation is expected in 2022 and serial production in 2024.
The development of larger turbines has accelerated in the last few years. In 1985, offshore wind turbines were below 1 MW with rotor diameters of around 15 meters. More than two decades later the average capacity reached 2.5 MW in 2012 with rotor diameters of 100 meters, while it took only 4 years to almost double that number again to 4.8 MW in 2016. The growth has since continued and the average offshore wind turbine capacity exceeded 8 MW for the first time in 2020 despite the pandemic. It has reached 10.4 MW in 2020 based on latest data from ordered capacity, according to WindEurope, the industry association.
It makes perfect sense to build larger turbines from a technical perspective. While the wind energy available for conversion to electricity largely depends on the wind speed cubed, it is also proportional to the length of the blade. Doubling the blade length would lead to a doubled rotor diameter and a quadrupled swept area, which means more wind is captured and higher power generating capacity is possible for a single turbine. This makes operation particularly effective in offshore environments where turbines take advantage of winds that are stronger and blow more consistently than land-based wind, which explains why offshore projects are generally in larger scale, and onshore wind turbines are smaller in size. Siemens Gamesa’s market-leading onshore wind turbine SG 5.8–155 has a maximum capability of only 6.6 MW, while GE’s largest version available is 6 MW.
From an economic point of view, installation, operation and maintenance (O&M) costs fall with larger turbine sizes via economy of scale according to International Renewable Energy Agency (IRENA), while larger turbines, equivalent to higher hub height (rotor’s height above platform) and larger swept areas, enable wind farms to move further offshore to exploit stronger and more stable wind resources due to reduced wind turbulence, which results in an increased capacity factor, i.e. higher realistic power output per unit. While it is true that larger turbine requires larger nacelles, more robust structure and different crane system, the IRENA report suggests that it does not lead to a proportional increase in the cost of other turbine components and thus the increase in cost on a per unit basis is not as significant as might be expected. The report also shows that turbine prices fell by 44–78% for the past decade to a range of USD 560–830/kW. The decline in production cost, driven by economy of scale, technological development and learning effect, might have also encouraged turbine makers to invest in upgrading their wind turbines in the face of greater competition, as developers seek to maximize cost savings by having larger turbines that harness more energy.
Morten Pilgaard Rasmussen, head of offshore technology at Siemens Gamesa, told Greentech Media,“I think the technology can just keep going on and on, but the market will tell us when it’s no longer feasible.”
While the race among global players to build larger turbines continues, it will further intensify when the technology of floating offshore wind turbines advances and production cost reduces to competitive level. The average water depth for offshore wind projects in 2019 was only 33 meters, while it is said that close to 80% of offshore wind resource potential is in outlying ocean waters deeper than 60 meters, where the world’s strongest and most consistent wind blows and where floating turbines can access. Hywind Scotland, commissioned in 2017, is the world’s first commercial floating offshore wind project in deep water environment of 95–129m with five 6 MW turbines, before Vesta installed last year the largest floating turbines for this moment— five 9.5 MW turbines—in Kincardine wind farm off Scotland at water depths ranging between 60 and 80 meters.
The largest wind turbines in the next decade will likely be out of our sight, installed far away on the horizon.
