The Repowering Mission: Breathing New Life into Our Aging Wind Turbine Fleet

Through the work of repowering, wind farms facing the end of their lifespan in the next five years could last to 2050 and beyond.

The global wind turbine fleet, which, according to data from the Global Wind Energy Council, currently stands at about 341,000, faces an important reality as the years go by – many of its units are getting old. The industry average for a wind turbine’s lifespan is typically placed at 20-25 years. Projects that were built in the early 2000s already face the possibility of decommissioning in the coming years, unless their owners can find the right scenario to give them new life.

The Mendota Hills wind farm in Lee County, Illinois. Credit: Dori, CC BY 2.5, Wikimedia

The Mendota Hills wind farm in Lee County, Illinois. Credit: Dori, CC BY 2.5, Wikimedia

Known as repowering, the updating of wind turbines at existing wind farms can be accomplished by either replacing older wind turbines with fewer units with a higher capacity or swapping out the parts in the original turbines with new, more efficient technologies.

In a report released in March, London-based Energy and Climate Intelligence Unit (ECIU) said that there are about 60 onshore wind farms across England, Scotland and Wales that will pass their 20-year operations marks within the next five years. Those projects represent 440 MW of installed capacity from about 750 wind turbines. ECIU said that repowering the group could see the installation of as much as 1.7 GW of installed capacity.

According to the report, the Delabole wind farm in Cornwall, England, was placed in service in 1991, and was repowered between 2009-2011. The installed capacity increased from 4 MW to 9.2 MW as a result of the repowering project. In addition, a repowering project that took place at the Carland Cross wind farm, also in Cornwall, increased the installed capacity from 6 MW to 20 MW in 2013.

In North America, the average age of the wind turbine fleet will reach 14 years by 2030, according to IHS Markit. That means about a quarter of the fleet will have passed its expected lifespan at that time.

Some of those units already have begun the repowering process.

Leeward Renewable Energy, LLC and GE Renewable Energy in January said they completed the repowering of Leeward’s combined capacity 136-MW Sweetwater 1 & 2 wind farms in Nolan County, Texas. Sweetwater 1 & 2 have been in operation since 2003 and 2005, respectively.

Sweetwater Texas wind turbine. Credit: Drew Stephens CC 2.0 Wikimedia

“For Leeward, and especially for the market more broadly, you will see more of these projects where we’re going to bring today’s new and improved technology to some existing, proven sites that have been around for a while,” Leeward CEO Greg Wolf said.

According to Wolf, the repowering included updating the GE 1.5 S units at Sweetwater 1 and GE 1.5 SLE units at Sweetwater 2. They left the towers in place at both projects, and replaced the entire nacelles and added bigger blades for better efficiency at Sweetwater 1. At Sweetwater 2, they left the nacelles in place and replaced the drivetrains in the units and added bigger blades.

“It’s pretty amazing in 10-12 years how the efficiency of the equipment has become better, and certainly with the blades, which are longer and bigger, better designed and lighter — all of that enables these projects to deliver the improvement that we’re getting on the investment in the repower,” Wolf said.

That investment also translates to a much longer life for the repowered project. Wolf said Sweetwater 1 & 2 likely will see a longer new lifespan than the 20- to 25-year estimate for older projects.

“We did extensive engineering work on the existing project infrastructure — the foundations, electrical system and towers — and the engineers confirm that these projects have plenty of useful life left in them,” Wolf said. “Our expectation is that these projects, like many new projects today, will have a 25- if not 30-year life going forward from Jan. 1, 2018.”

Wolf said the company has plans to continue repowering projects in its portfolio through at least 2020. The company has 19 projects in the U.S. with a combined installed capacity of 1.7 GW. In March, Leeward announced that it selected Siemens Gamesa to supply 29 SG 2.6-126 wind turbines for the repowering of the Mendota Hills wind farm in Lee County, Illinois. Those units will replace the 63 original, legacy Gamesa wind turbines, bringing total project capacity to 76 MW, up from about 50 MW.

Jose Antonio Miranda, CEO Onshore Americas for Siemens Gamesa Renewable Energy, said in a statement that the Mendota project is the company’s first full-scale repowering in the U.S.

Ontario, Canada-based OMERS Infrastructure Management Inc. in March sealed a deal to acquire Leeward from affiliates of ArcLight Capital Partners, LLC. Wolf said in a statement at the time that Leeward will continue operating its wind farm portfolio and “executing on innovative repowering initiatives.”

Support for Repowering

While improving the technical capabilities of a wind farm are central to repowering, the wind farm owners need to find themselves in an environment that is favorable to the effort.

Wolf said that working with GE Energy Financial Services (EFS) was important to the repowering work at Sweetwater 1 & 2.

“GE EFS was a critical part of our overall project advancement in the sense that we needed to have a financing partner relative to the tax equity,” Wolf said. “We bought safe harbor turbines at the end of 2016 so that the kits that we bought for these projects enabled this project to be production tax credit-qualified.”

In addition, Leeward was able to secure an offtaker for the repowering project at the Mendota Hills wind farm, an agreement Wolf said was central to the overall investment. Data center provider Digital Reality in December 2017 agreed to purchase 276 GWh of electricity from the Mendota Hills project annually.

The outlook for repowering opportunities in England is currently hindered by an unsupportive political environment. ECIU said in its report that, with the closure of the Renewables Obligation scheme to new entrants last year and current policy prohibiting new large-scale wind, “the U.K.’s ability to refresh its ageing wind fleet is compromised.”

Wales and Scotland, however, show some promise. ECUI said that 80 percent of U.K. capacity that will reach retirement age by 2023 is located in Wales and Scotland, where more community and government support exists.

Data Points

• Number of Wind Turbines in the Global Fleet: 341,000 (Source: Global Wind Energy Council)

• Number of Parts in a Wind Turbine: 8,000 (Source: Global Wind Energy Council)

• Average Lifespan of a Wind Turbine: 20-25 Years

• Wind Turbine Capacity that Will Pass 20 Year Operations Mark by 2023 in UK: 440 MW (Source: Energy and Climate Intelligence Unit)

• Average Age of North American Wind Turbine Fleet in 2030: 14 Years (Source: IHS Markit)

• Number of Months to Build a 10-MW wind farm: 2 (Source: Global Wind Energy Council)

• Average O&M Cost of a Wind Turbine During First 10 Years of Operation: US $44,000 (Source: IHS Markit)

• Average Capacity of Onshore Wind Turbines Installed in the UK in 2018: 2.5 MW (Source: WindEurope)

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