Aging Wind Farms Are Repowering with Longer Blades, More Efficient Turbines

Jobs and a thriving industry are growing up around the ‘repowering’ of existing wind farms, as technology upgrades increase their renewable energy production.

A crane lifts blades to be added to a wind turbine. Credit: Dennis Schroeder/NRELA crane lifts a blade being attached to a wind turbine. Credit: Dennis Schroeder/NREL
Technological advancements are making wind turbines more efficient and blades more aerodynamic. "We can tweak it so it becomes a different machine," one official said. Credit: Dennis Schroeder/NREL

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Old wind farms that have towered over the same fields for more than a decade may be generating more power now than ever before.

As America’s biggest wind farms age, their owners are starting to “repower” them with more efficient turbines, new electronics and longer, lighter blades that can sweep more wind with each rotation. The result is a thriving new industry, new jobs and more renewable energy.

New blades and technology updates have completely “revitalized” two Leeward Energy wind farms near Sweetwater, Texas, saving the company money and allowing the farm to generate more energy, said Leeward CEO Greg Wolf.

“In a sense, we have a whole new wind farm,” he said.


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Last year, the U.S. wind industry completed 15 partial repowering projects totaling 2,136 megawatts, according to the American Wind Energy Association. (To put that in perspective, the entire U.S. wind industry added about 7,000 megawatts of wind power capacity in 2017.) As the market for wind continues to expand and technology keeps dropping in cost and becoming more efficient, renewable energy companies around the world are starting to update their fleets.

“It’s extending the life of these projects without having to build a new wind farm, by taking advantage of existing infrastructure, project locations and power purchase agreements to help save costs,” said Celeste Wanner, research analyst for AWEA. “Repowering benefits everyone with lower cost to consumers and higher performance of the turbines.”

Saving Money, Raising Power Production

When wind development started to take off a few decades ago, major companies gobbled up some of the best sites for wind production. But turbine efficiency continues to improve, and costs have dropped by two-thirds since 2009.

“The energy capacity factor of the average turbine has jumped from 30 percent in the early 2000s to anywhere from 40 to 50 percent now,” Wanner said. “Compare that to a typical coal plant, which has about 54 percent.”

With the advancement of technology—and incentives in the form of federal tax credits—more wind farms are now choosing to replace blades and turbine parts, rather than the entire 300-foot structures.

An illustration shows some of the mechanisms inside wind turbines. Repowering can include new internal technology, as well as longer, lighter blades. Credit: Siemens.
An illustration shows some of the mechanisms inside wind turbines. Repowering can include new internal technology, as well as longer, lighter blades. Credit: Siemens.

The National Renewable Energy Laboratory has estimated that U.S. wind repowering investments like these could reach $25 billion a year by 2030.

MidAmerican Energy recently announced plans to spend $1 billion repowering 700 older turbines across Iowa by replacing blades and rotors, which would reportedly allow each turbine to create between 19 and 28 percent more energy.

Some developers are trading fleets of older turbines for fewer, more advanced ones that require less maintenance and offer more energy generation. Leeward’s Mendota wind farm in Lee County, Illinois—the state’s largest wind farm, about 100 miles west of Chicago—is replacing 63 older Siemens Gamesa turbines with 29 new ones. The company says the process will create 115 construction jobs, plus maintenance jobs once it’s complete at the end of this year, and boost capacity from 50 megawatts to 76 megawatts.

Wolf said his company’s Texas upgrades have already saved Leeward up to 20 percent of its cost of producing power, and he expects major savings in Illinois as well.

GE equipment is repowering two Leeward Energy wind farms near Sweetwater, Texas. Credit: GE
Upgrades to two Texas wind farms have saved Leeward up to 20 percent of its cost of producing power, Wolf said. Credit: GE

Major wind turbine manufacturers like GE and Siemens have been focusing on wind repowering efforts in the last two years, and they’re seeing benefits to their business. Along with turbines, Siemens makes blade tip extensions to improve energy generation in lower-wind areas and has developed upgrades that make turbines more aerodynamic, said Justin Torpey, group lead for modernization at Siemens in Denmark.

“What we’re doing is ramping up so we can get better power at lower winds,” Torpey said. “We can tweak it so it becomes a different machine.”

According to GE, the largest wind turbine installer in the U.S., repowering wind turbines can increase a fleet’s output by 25 percent.

Improving Wind Power’s Bottom Line

The federal renewable energy production tax credit has sweetened the deal for U.S. wind farm operators looking to upgrade their fleets, though it’s phasing out at the end of 2019. A wind farm can qualify as long as at least 80 percent of the property’s value is new—which means developers can more cheaply repower existing turbines without replacing them.

With the credit, AWEA expects that wind energy can grow to supply 10 percent of U.S. electricity by 2020.

By updating, developers are also reinvesting in the communities around wind farms, like Illinois’s Lee County. “We share with landowners on leases, so for us it’s not just a benefit for us but each of the communities were in benefit as well,” Wolf said.

These upgrades are also creating jobs and growing all aspects of the U.S. wind industry—from manufacturing to construction to maintenance, Wanner said.

After the old turbines are deconstructed, some companies benefit again from recycling the turbine parts or sending them to other countries to use.

“Over the course of the next two years we should be seeing more repowerings as projects get older and it makes more sense to upgrade,” Wanner added. “It’s really making wind power truly renewable.”

Read this next: Near Sweetwater, Texas, renewable energy means jobs, but climate change can be a challenging conversation.