Huge new turbines could let biggest UK wind farm do more with less

It’s almost an ironclad law: Over time, wind turbines get taller, better, and more cost-effective.

A new proposed project in the U.K. demonstrates that. ScottishPower recently announced its intention to repower the U.K.’s largest onshore wind farm, a process that will involve replacing old turbines with state-of-the-art new ones. Once that is done, the wind farm will produce twice as much power with almost half the number of turbines.

The Whitelee wind facility, near Glasgow, was completed in 2008. The developers installed 140 turbines that stood 360 feet tall at the highest blade tip and could generate 2.3 megawatts each. By 2013, the site had been expanded with 3-MW turbines that stood 459 feet. Since then, Whitelee has produced up to 539 MW from its 215 turbines, storing some of that in a 50-MW battery on-site.

If the forthcoming upgrade gets regulatory signoff, the old turbines will be taken down and in their place will rise 124 new ones, measuring 787 feet tall and producing around 7 MW apiece. Collectively, they will be able to generate more than 1 gigawatt of carbon-free power when the wind blows fiercely.

“Repowering allows SPR [ScottishPower Renewables] to reuse existing site infrastructure and take advantage of new technologies resulting in increased electricity generation and ultimately, increased security of supply,” the company noted in a scoping document.

It’s a striking example of how far this clean energy technology has advanced in recent decades. Modern turbines have pushed to incrementally higher heights and broader wingspans, allowing them to generate far more electricity than their predecessors — and to do so at a cheaper unit price. This evolution supports onshore wind’s position as the cheapest of all the electricity sources on an unsubsidized basis, per the latest analysis by the financial advisory firm Lazard.

Repowerings like Whitelee’s could help the U.K. and the European Union shore up their energy security as the natural gas supply chain remains in war-torn upheaval. And while the U.S. government currently seeks to thwart this affordable energy source, there are signs that repowerings could add significant capacity in the coming years.

Benefits and trade-offs of wind repowering

The main appeal of repowering is to access the much greater clean power generation — but there are other benefits, too.

“It doesn’t take twice as long to service a turbine that’s twice as big, and you don’t have to do two foundations — you only need to do one,” said Kaj Skov Nielsen, a longtime wind power specialist who helped set up the control system at Whitelee.

Installing a new turbine also gives project owners an easy opportunity to add state-of-the-art sensors, Nielsen said. New sensors can detect birds and bats and slow the blades’ rotation to protect them. Others can spot potential mechanical issues, like debris that could cause problems in the gearbox, before they become catastrophic.

Older turbines have control systems that can stop the blades if they detect a fault. Newer systems can slow the rotation to a safe level based on the specific fault that is happening, Nielsen said, eking out more generation without endangering the equipment — ​“it’s a totally different game.”

That’s not to say repowering is easy. Larger equipment may exceed the weight limits on the roads and bridges to the project site, or height limits on underpasses along the route, Nielsen noted. Developers need to weigh the cost of upgrading that transportation infrastructure against the alternative of shipping in pieces and assembling them on-site, which adds more work on the back end. A developer also needs to strengthen foundations to support the weight of much larger turbines.

ScottishPower still needs consent from the Scottish ministers for the repowering, so it will go through a detailed assessment for impacts on the community and the environment. The repowering project has two big advantages in that process, compared with a brand-new project: It already secured permission to build many more turbines on the same land, and it would upgrade capacity without expanding into undeveloped countryside.

ScottishPower, for its part, has tried to make Whitelee welcoming to the broader community. The energy company acquired the site after it had been used for commercial logging and has invested in wide-scale restoration of the underlying peatland ecosystem. People can bike or hike around the premises, take guided bus tours, and enjoy the views from a visitor center that touts its ​“delicious cakes” from local vendors. The power company markets it with the hashtag #MoreThanAWindfarm.

Can the U.S. get on the wind repowering train?

Turbines of the size proposed for Whitelee have just started getting installed around the world, said BloombergNEF wind analyst Harrison Sholler. Chinese manufacturers have been pushing the boundaries of onshore turbine size, but those units are typically shut out of Europe and the U.S. because of geopolitical concerns. Instead, developers in those regions turn to manufacturers including Siemens Gamesa, Vestas, and Nordex, all of which now sell 7-MW onshore wind turbines; or GE, which has onshore models up to 6 MW.

A project in Brazil’s Bahia state installed a new 7-MW turbine last fall, touting it as the largest onshore turbine in the Americas.

“It’s established technology in the sense that they’re not that different from a 6-MW turbine, for example,” Sholler said. ​“They’re considered by the industry to be proven at scale.”

The U.S. might not have any turbines that big yet, but it does have plenty of installed turbines of the smaller vintage that ScottishPower seeks to replace. The U.S. average onshore wind turbine capacity has steadily ticked up from 0.8 MW in 2000 to 1.8 MW in 2010 to 3.5 MW in 2024, per the most recent accounting by Lawrence Berkeley National Laboratory. The country’s first 6-MW-turbine project came online that year in Oklahoma.

Of the 86 GW of new wind capacity BNEF expects the U.S. to build over the next decade, 10 GW will come from repowering, said Sholler. ​“Towards the early to mid-2030s, we expect repowering activity to ramp up as some of the larger wind farms are reaching the end of their operational life,” he noted.

BNEF expects the Northwest and Midwest will build the most repowered wind capacity in the next 10 years, with significant capacity popping up in Texas, California, and the mid-Atlantic. In California, repowerings will provide pretty much all new onshore wind capacity in that period, Sholler said, because all the good sites for onshore wind farms got developed decades ago, starting when the state initiated a subsidy in the 1980s.

That said, the largest U.S. repowering on BNEF’s radar for the next decade clocks in at just over 200 MW, a far cry from the projected 1 GW at the refurbished Whitelee.

“I don’t think we’re at the stage of market maturity where we’re starting to see those larger-scale projects start to repower in the U.S.” Sholler said. ​“But we will get there eventually.”