The 169 wind turbines spinning off the Yorkshire coast in Great Britain are a feat of engineering: each 8-megawatt model built by the Danish company Ørsted can power a house for 24 hours with a single rotation of its 81-meter blades.
Dozens of kilometers to the north, rival wind farm developer SSE is already upping the ante with its newest turbines, where a single turn of the 107-meter blade can power a house for two days.
The leap in the size of offshore wind turbines, whose blades can reach heights greater than New York's Rockefeller Center and supply electricity to millions of homes, reflects the fierce race for scale over the past decade or more.
The rapid pace of evolution stimulated by wind farm developers and turbine manufacturers has helped drive down costs and proved that the industry can play an important role in decarbonizing the energy system. But critics fear that the race is starting to do more harm than good, as supply chains struggle to catch up and questions arise about the technical risk and profitability for turbine manufacturers.
"The acceleration of development cycles for new wind turbine models in recent years has not helped," said Christoph Zipf, spokesman for trade group WindEurope. "We need to slow down."
Many industry executives want an end to the era of turbine growth, with a period of model standardization seen as the best way to help developers meet rapid growth targets.
Although a limit on turbine size has also been seriously discussed in the industry, many developers still find it difficult to resist the lure of the higher efficiencies being touted. Turbine producers also face continuous competition for larger machines, especially from Chinese rivals.
From the first models in the 1990s of less than 1 megawatt, today turbines are being developed with a capacity of 18MW or more, with blades longer than soccer fields, supported by masts that rise more than 100 meters above the surface of the water.
Getting more electricity from each turbine has helped reduce wind energy costs by 60% in the decade to 2021, according to the International Renewable Energy Agency.
However, the rapid pace of development brings challenges, for example for the ship manufacturers who install the turbines, as well as for other parts of the supply chain that need to adapt to the huge increases in size and weight.
"We're now talking about nacelles [part of the turbine] that weigh 800 to 1,000 tons," said Anders Nielsen, chief technology officer at Vestas, a leading turbine manufacturer. "You need to reinforce the quays [to deal with the situation]."
A report by consultancy Wood Mackenzie said this month that around half of the world's installation ships are about to be retired because they were not designed to cope with the latest turbine models, with around $13 billion in investment needed for replacements.
But vessel owners have already been hurt by investing heavily in new models, only to find that they were quickly outclassed, said Torgeir Ramstad, managing director of the installation division of offshore vessel owner Cyan Renewables. "We [Cyan] will now only build on the basis of long-term contracts with developers," he said.
The rapid pace of development means that models are being introduced before the performance of existing models has been observed over the long term, raising questions about whether potential problems are understood.
"I don't know of any other industry that has moved at this pace in terms of bringing new models to market before there has been any real experience of services at the previous levels," said Professor Simon Hogg, who holds the Ørsted Chair in Renewable Energy at Durham University in Britain. "This has put a lot of risks on the industry."
Renewable energy insurer GCube said in a May report that machines larger than 8MW were presenting problems more quickly than their smaller counterparts.
Meanwhile, the industry's finances are under pressure. Turbine manufacturers have suffered steep losses in recent years as they try to produce new models while keeping prices down and struggling with warranty provisions.
Developers are also now under pressure from inflation and high interest rates. Swedish developer Vattenfall suspended a new project in the North Sea in July, while Iberdrola and Shell are also terminating deals in the United States.
Slowing down the development of new turbine models and instead focusing on standardizing existing ones may be the best way for the industry to grow and meet ambitious clean energy targets, some believe.
Jochen Eickholt, chief executive of turbine manufacturer Siemens Gamesa, said that while upsizing is technically possible "much larger turbines would need a suitable infrastructure that does not yet exist, including ports and ships".
Siemens Gamesa is facing technical problems with its latest onshore wind turbines, as well as challenges in increasing offshore wind power. "The priority should be to ensure a sustainable and profitable future for the sector, while meeting increasing targets around the world," said Eickholt.
Ben Backwell, chief executive of the Global Wind Energy Council, a sector body, believes that the industry should now produce existing models on an industrial scale, allowing companies to capitalize on investment in current models.
"It is also important that projects can benefit from investments in installation equipment and infrastructure such as ships and cranes, without these constantly becoming obsolete due to the constant increase in turbine size," he said.
However, it's not easy to focus on existing models, given the fierce competition in the market. "If General Electric [launches a larger model], Siemens Gamesa will do the same immediately. Then Vestas will come under pressure to launch another one," said Shashi Barla, head of renewable energy research at consultancy Brinckmann.
The race for size among Chinese manufacturers adds to this competitive pressure. Offshore turbine producers in China could start to make more significant inroads into the western offshore market as costs in the US and Europe rise, Barla said.
Cyan's Ramstad believes that a limit on the size of turbines would ensure standardization, preventing the market from pushing the boundaries. "We desperately need this electricity, and the way to build it quickly is to industrialize, rationalize and standardize," he said.
Wood Mackenzie said in her report that a temporary cap, lasting at least ten years, would "give suppliers and investors confidence in their new investments".
"Ultimately, the most important factor is not the size of the cap, but the fact that a cap is imposed at all," he added.
Many industry players do not support a cap, and some worry about the possibility of unintended consequences.
"What we need to see is a progressive evolution, rather than a revolution, and avoid implementing measures that could stifle innovation," said Rob Anderson, director of wind energy projects at Vattenfall off Norfolk in the east of England.
Iberdrola, one of the world's largest wind farm developers, supports the slowdown in new models, although it doesn't believe a limit is necessary. With better profit margins in the future, "we are confident that the industry will experience a new impulse and that larger sizes will be developed," he said.
Nielsen, from Vestas, has a similar opinion, emphasizing the need for responsible development. "The only way to really meet market demand is to slow down the growth of turbines," he said, adding: "This industry needs to mature, and everyone has to make money in the supply chain for it to last."