ScottishPower wants to tear down 215 turbines at the UK's largest onshore wind farm and replace them with 124 machines rated around 7 MW each — pushing output past 1 gigawatt from fewer than half the current units.

The Whitelee facility near Glasgow, completed in 2008, currently hosts 140 turbines at 2.3 MW and 360 feet to blade tip, plus an expansion added by 2013 of 3-MW machines standing 459 feet. The site produces up to 539 MW and stores part of it in a 50-MW on-site battery. The repowering proposal, announced by ScottishPower, would install turbines measuring 787 feet tall — pending consent from Scottish ministers.

More power, less steel on the ground

For the circular economy desk, the appeal is straightforward: repowering extracts twice the generation from existing sites, foundations and grid connections rather than greenfield land. "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 stated in a scoping document.

Kaj Skov Nielsen, a wind specialist who helped set up Whitelee's control system, put the operational math bluntly: "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."

New builds also carry modern sensing. Nielsen said contemporary systems detect birds and bats and slow blade rotation to protect them, and can spot mechanical issues such as gearbox debris before they turn catastrophic. Older controllers simply stop blades on fault detection; newer ones modulate rotation to a safe level per specific fault, recovering generation without risking equipment. "It's a totally different game," he said.

The decommissioning and logistics bill

Repowering is not a swap-in exercise. Nielsen flagged the constraints: larger components may exceed weight limits on roads and bridges or height limits on underpasses en route, forcing developers to weigh infrastructure upgrades against shipping in pieces and assembling on site. Foundations also need strengthening to carry much larger machines.

Whitelee carries two procedural advantages over a new-build application, however. The site already secured permission for more turbines on the same land, and the upgrade adds capacity without extending into undeveloped countryside. ScottishPower still faces a detailed environmental and community impact assessment before ministers rule. The company has also invested in large-scale restoration of the site's peatland ecosystem since acquiring the land, previously used for commercial logging.

A 7-MW class going global

Turbines of this size have only just begun deployment worldwide, according to BloombergNEF wind analyst Harrison Sholler. Chinese manufacturers lead on size but are effectively shut out of European and US markets on geopolitical grounds, leaving developers there to buy from Siemens Gamesa, Vestas and Nordex — all now selling 7-MW onshore platforms — or GE, whose onshore models reach 6 MW. A project in Brazil's Bahia state installed a 7-MW turbine last fall, billed as the largest onshore machine 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 US pipeline is smaller — for now

The US fleet mirrors the vintage ScottishPower wants to replace. Average onshore turbine capacity rose from 0.8 MW in 2000 to 1.8 MW in 2010 and 3.5 MW in 2024, per Lawrence Berkeley National Laboratory, with the country's first 6-MW-turbine project coming online in Oklahoma last year.

Of the 86 GW of new US wind capacity BNEF expects over the next decade, 10 GW will come from repowering. "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," Sholler said. BNEF projects the Northwest and Midwest will lead, with significant additions in Texas, California and the mid-Atlantic. In California, repowerings will account for nearly all new onshore wind capacity in the period, since prime sites were developed decades ago under a subsidy launched in the 1980s.

The scale gap remains wide: the largest US repowering on BNEF's 10-year radar is just over 200 MW, against the projected 1 GW at 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."

The decisive milestone for Whitelee now sits with the Scottish government's consent process — the community and environmental assessments that determine whether 215 legacy turbines come down and a 1-GW fleet rises on the same foundations.