Second Wind: This Squad Is Rejuvenating America’s Wind Turbine Fleets, Not Tearing Them Down

Nobody blinks when a decades-old office tower gets a facelift. New elevators, heating, and plumbing give the owner a high-performing, future-proof building at a fraction of the cost of building new - and eliminate much of the new construction red tape. Doing the same for another kind of skyscraper, an aging wind turbine, used to be far more rare. Owners could swap out aging parts for replacements, but they rarely changed the machine's silhouette. That changed in 2016, when GE Vernova proved that you could also fit existing wind turbines with the latest and greatest technology to generate more energy, quickly.

Lauren Wyant, an Illinois-based Wind Services commercial leader at GE Vernova, remembers the day when she and her engineering team proved it could be done. It was a midsummer morning in Texas, and the first cranes were rolling into a large onshore wind farm to revamp its turbines by upsizing their rotors - the three blades connected by a hub. Wyant recalls that the team had "done everything we needed to do to feel comfortable on paper." Their homework paid off, and within months, they'd beefed up all 74 turbines on the site, chalking off 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,'" recalls Wyant.

A decade later, GE Vernova has done the same for well over 6,000 wind turbines across the United States, practically writing the wind industry's repowering playbook. Just as with a high-rise retrofit, its engineers can preserve the main infrastructure of wind turbines nearing 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 determine performance, with GE Vernova's workhorse technology.

GE Vernova CEO Scott Strazik noted in the company's most recent Annual Report that its installed base of more than 59,000 turbines represents a massive 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 has many advantages over the traditional scrap-and-rebuild method. These advantages rest on four principles: increased production, improved reliability, extended life, and lower operation and maintenance costs. A partially repowered wind turbine is back up and running in just a couple of days, rather than months. That allows a wind farm operator to sell tens of thousands of "extra" megawatt-hours of carbon-free generation. Partial repowering also often spares owners and operators from the painstaking paperwork required for new projects, such as decommissioning permits and modified grid agreements.

Front-end modifications to the turbine focus on upsizing the rotor, with new, longer blades that catch lower-speed winds, allowing them to generate more electricity. The process also typically extends the operating life of turbines by upwards of 20 years.

Repowering helps rejuvenate fleets of older 1-MW turbines like these on a wind farm in Texas. Images credit: GE Vernova

Helping to spearhead GE Vernova's wind repowering mission with Wyant was David Ash, a veteran wind product manager based in Schenectady, New York. Ash, who learned the art of repowering from his experience with heavy-duty gas turbines in the 1990s, laid down the gauntlet 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 rose to 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 makes sense, as new gas turbines and supporting infrastructure such as roads, foundations, and substations can easily run 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 grew rapidly in the early 2010s, GE Vernova's engineers wondered if they could bring 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 running the numbers on the rotors, calculating how increasing blade length would increase their swept area. Their math checked-out, but it presented an engineering conundrum. Could they supersize the blades if everything else - the turbine's foundations, steel tower, and machine head - stayed the same?

"That 15-year-old infrastructure needed to withstand this new larger rotor," says Ash. Thanks to rapid advances in manufacturing and material science, wind turbine blades were getting 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 churning out insights about fatigue load and aeroelasticity from mountains 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 figured out 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 diverse geography was 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 gurus, and mechanical experts to fine-tune their repowering formula.

It didn't take long for the design to obtain 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 landing 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 kicked it up a gear 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 come through with the goods. "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 continue to evolve, 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 keen to emphasize 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."