No one raises an eyebrow when a decades-old office building receives a major renovation. Fresh elevators, HVAC, and plumbing give the owner a high-performing, future-proof property at a fraction of the cost of new construction — and sidestep much of the red tape that comes with building from scratch. Applying the same approach to another type of skyscraper, an aging wind turbine, was once far less common. Owners could replace worn-out parts with new ones, but they seldom altered the machine’s overall profile. That shifted in 2016, when GE Vernova demonstrated that existing wind turbines could also be equipped with the newest and most advanced technology to produce more energy, and to do so quickly.

Lauren Wyant, an Illinois-based Wind Services commercial leader at GE Vernova, recalls the day she and her engineering team proved it was achievable. It was a midsummer morning in Texas, and the first cranes were arriving at a large onshore wind farm to overhaul its turbines by enlarging their rotors — the three blades joined by a hub. Wyant remembers that the team had “done everything we needed to do to feel comfortable on paper.” Their preparation paid off, and within months, they had upgraded all 74 turbines at the site, completing the world’s first-ever “partial repowering” of an entire wind farm that included an increase in rotor diameter. “We had our proof to say, ‘We can do this,’” Wyant recalls.

A decade later, GE Vernova has carried out the same work on well over 6,000 wind turbines throughout the United States, effectively authoring the wind industry’s repowering playbook. Much like a high-rise retrofit, its engineers can retain the core infrastructure of wind turbines approaching the end of their original design life — a turbine’s concrete foundations, steel towers, and electrical equipment — while upgrading the rotor and drivetrain, the components that govern performance, with GE Vernova’s workhorse technology.

GE Vernova CEO Scott Strazik observed in the company’s most recent Annual Report that its installed base of more than 59,000 turbines constitutes a substantial strategic advantage: “We see an immediate opportunity to repower tens of gigawatts of aging assets … delivering up to a 20% to 30% increase in annual energy production for our customers using existing grid interconnections. GE Vernova is uniquely positioned and ready to execute on this challenge.”

Beyond Scrap and Rebuild

Partial repowering offers numerous benefits compared with the conventional scrap-and-rebuild approach. These benefits are built on four principles: greater production, enhanced reliability, extended life, and reduced operation and maintenance costs. A partially repowered wind turbine is back in service in only a couple of days, rather than months. That enables a wind farm operator to sell tens of thousands of “extra” megawatt-hours of carbon-free generation. Partial repowering also frequently spares owners and operators from the arduous paperwork demanded by new projects, such as decommissioning permits and modified grid agreements.

Front-end modifications to the turbine center on enlarging the rotor, with new, longer blades that capture lower-speed winds, enabling them to produce more electricity. The process also typically extends the operating life of turbines by upwards of 20 years.

Helping to lead GE Vernova’s wind repowering mission alongside Wyant was David Ash, a veteran wind product manager based in Schenectady, New York. Ash, who learned the craft of repowering through his experience with heavy-duty gas turbines in the 1990s, issued the challenge to Wyant and the team in mid-2016.

“I wanted the biggest rotor possible without tipping the tower over or digging trenches next to the turbine,” he says. “I left it to them to figure out how big.”

Wyant and her team met the challenge. “We’d already learned so much about how wind impacts a turbine in the previous decade and embedded that into our technology and our fatigue assessments,” she explains. “We were ready to go bigger and better.”

A New Lease on Life

GE Vernova engineers have been repowering thermal power plants for years. This stands to reason, as new gas turbines and supporting infrastructure such as roads, foundations, and substations can easily reach into the hundreds of millions of dollars.

“You’d never tear down gas turbines and put larger ones in their place,” says Ash. “You continually upgrade them and improve their performance over their life cycle.”

As renewables and commercial wind power generation expanded rapidly in the early 2010s, GE Vernova’s engineers wondered whether they could apply the same philosophy to onshore wind fleets. “We asked ourselves: Why are we letting these assets run out?” says Ash. “Could we extend their lifetime and also improve their performance capabilities?”

The engineers began crunching the numbers on the rotors, calculating how increasing blade length would enlarge their swept area. Their math held up, but it raised an engineering dilemma. Could they supersize the blades if everything else — the turbine’s foundations, steel tower, and machine head — remained unchanged?

“That 15-year-old infrastructure needed to withstand this new larger rotor,” says Ash. Thanks to swift advances in manufacturing and material science, wind turbine blades were growing larger, but also lighter.

“In 2016, we were light-years ahead of where we were in 2006,” says Dan Messier, the Schenectady, New York–based current product line leader for Repower.

Finding a Formula

GE Vernova turned to Wyant and the team, who set about answering Ash’s “How big can we go?” question. Very soon, they were generating insights about fatigue load and aeroelasticity from vast stores of historical data.

“We worked out we could go from 77-meter rotor diameter to 87-meter diameter to start, and eventually we made it to 97 meters,” says Wyant. They calculated how to pitch and yaw the longer blades for optimal safety, mechanical load, and power output. They determined they’d also need to upgrade rotor components downstream of the spinning blades, such as the pitch bearings, the main shaft, and the gearbox.

America’s varied geography presented another challenge. “How do you take 10 years of different wind speeds in Texas, Nebraska, or Iowa and model it for the next two decades?” asks Wyant. The team consulted greenfield engineers, component specialists, and mechanical experts to refine their repowering formula.

It didn’t take long for the design to secure third-party certification. “It’s not just our team that believes in this,” says Wyant. “It’s a real product that customers can show their bank manager.”

In early 2017 the floodgates opened, with repowering projects arriving on Wyant’s desk from all across the Lone Star State. In the 18 months after July 2016, they repowered 1,100 turbines.

“We were off to the races,” says Ash.

They’ve accelerated since then. Today it takes just two days to partially repower a wind turbine with GE Vernova’s workhorse products, which are proven, repeatable technologies that are manufactured and validated at scale. Engineers and field crews can work on four or five turbines simultaneously, meaning a full wind farm could be entirely repowered within weeks. GE Vernova has helped owners and operators in Texas, Nebraska, California, and 14 other states extend the lifetime of wind farms and boost availability.

Ash never doubted that Wyant and the engineering team would deliver. “We’re 10 years down the line with repowering,” he says. “Lauren and her team said they’d demonstrate the structural capability of these things, and that’s exactly what they’ve done.”

Meanwhile, the repowering formula will keep evolving, says Wyant. “There are so many different baseline turbine models, which means we’ve developed many different flavors” of repowering, she says. “That just didn’t exist 10 years ago,” she adds. As a product manager, Messier is eager to stress that one thing hasn’t changed: “The repowered units were such high quality from the start,” he says. “That’s still the story a decade later.”

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