This is a feature from Windpower Monthly's November/December 2021 Insight Report. Click here to read the full edition
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With nearly 40GW of Europe’s wind turbines set to be at least 20 years old by 2025, the region’s wind industry is increasingly looking towards repowering to help meet renewable energy and decarbonisation goals.
Older wind farms are typically located on sites with strong wind resources that could be better exploited by replacing old machines with the latest, more efficient and higher-capacity versions. Developers repowering projects can also take advantage of grid and other infrastructure already in place.
“Europe is now starting to dismantle its first generation of onshore wind turbines,” said Giles Dickson, CEO of WindEurope, at a conference in November on end-of-life strategies for ageing wind farms. “It is crucial that we keep the sites going and replace the old turbines with new ones. They’re the sites with the best wind conditions, and the winds farms have become a well-established part of the local economy.”
“Repowering offers an important opportunity to increase capacity at appropriate sites by installing more efficient and technologically advanced turbines,” the Scottish government pointed out in its draft onshore wind policy statement published in October.
Scotland expects repowering to play an important role, alongside new development, in increasing its existing 8.4GW in onshore wind capacity by 8-12GW by 2030. Up to 2.5GW of operational wind farms in Scotland will reach the end of their consented lifetime in the next decade, the government notes.
Research conducted by RenewableUK in 2020 forecasts that repowering across the UK could contribute about 1.2GW to its new wind capacity by 2030.
Without repowering, some European countries could risk backtracking. Austria, for example, saw its installed wind capacity decline by 39MW in 2020 after bringing online only 25MW in new capacity and decommissioning 64MW.
A WindEurope analysis of 137 projects repowered in Europe to date shows the benefits of updating turbine technology. On average, the number of turbines in these repowered wind projects decreased by 27%, while installed capacity was doubled and electricity output tripled.
A growing number of countries in Europe are looking to repower older wind projects, from Denmark, a frontrunner in wind, to the Netherlands, Italy and Spain.
Focus on Germany
However, the most active European market for repowering is Germany, where about 16GW in wind farms will cease receiving 20-year tariffs under the EEG renewable energy law by 2025.
In 2020, Germany accounted for the majority of 345MW of repowering projects completed in Europe, although there was also repowering activity in Greece, Luxembourg and the UK, WindEurope data shows.
While the average rated capacity of wind turbines currently installed in Germany stands at 1.8MW, newer machines have an average output of around 4.2MW and the most up-to-date models can even reach 6MW, notes a spokesman for German wind energy association BWE.
Although Germany’s potential is sizeable, a company seeking to repower needs to go through the same permitting process required for new wind farms, which takes six years on average, according to the BWE. Politicians are aware of the problem, and all major political parties in the country agree permitting must be accelerated if Germany is to meet its climate commitments.
Streamlined permitting
Germany’s wind energy industry argues that developers seeking to repower wind farms should be allowed to go through a streamlined authorisation process. “By giving repowering preferential treatment, the energy output of already existing wind power plants could be increased swiftly and significantly,” the BWE spokesman says.
When it comes to delays for permitting of repowered projects, Germany is no exception to the rule. In many countries in Europe, repowered projects must go through an authorisation process that is little or no different from that for greenfield developments. Permitting is the largest obstacle to repowering, so streamlining the authorisation process will be essential, says Ivan Komusanac, an analyst at WindEurope.
Delays have come even though a European Union directive issued in October 2020 called for member states to approve or deny permits within two years for new projects and within one year for repowering — a deadline that is widely ignored.
Although towns that already host wind farms have become accustomed to their presence, engaging with the local community is also key to repowering, given that there may be concerns about issues such as the noise and visual impact of larger turbines, Komusanac adds.
Case-by-case basis
Repowering is not a one-size-fits-all solution. More than half of German capacity coming offline will not be eligible for repowering, estimates WindEurope, as environmental restrictions have been tightened since the first wind farms were built, and taller turbines will not be able to be used in all locations due to distance rules.
“For locations without repowering options — for example because the areas are outside currently defined priority areas or due to restrictive planning and licensing regulations such as extended distance requirements — continued operation is sometimes the only option for further use of the area and existing infrastructure,” the BWE notes.
End-of-life decisions for ageing wind farms are based on a variety of factors, including siting regulations, but also the cost of operations and maintenance (O&M), the market framework to support repowering or lifetime extensions and power prices.
WindEurope anticipates that the vast majority, or some 29GW of wind farms, of the more than 38GW of European wind farms projected to turn 20 or older in 2021-25 will continue operating in that period, often with lifetime extension measures such as replacing gearboxes or blades. Another 7GW will be fully decommissioned. A further 2.4GW will be decommissioned and subject to repowering, although the repowered wind farms are expected to be rebuilt with about twice the capacity, or some 5GW.
As the number of older turbines in Europe increases and projects progress through the development pipeline, repowering is expected to accelerate in the second half of the decade, even if current restrictions continue.
Lasting longer
Another reason for not replacing more old turbines with new ones in the near term is that wind turbines are simply lasting longer than had been expected. This has allowed many project owners to postpone the decision to repower or decommission until a later date.
An example of this is Denmark. As part of a 2018 energy agreement the government illustrated plans to cut the number of operating wind turbines from about 4,300 at the time to 1,850 by 2030 as projects exited support schemes or were no longer financially viable. However, the deadline was pushed back to 2040 after the operational life of turbines was found to be longer than initially planned.
In a 2020 report, the Danish Energy Agency (DEA) found that the average economic life for existing onshore turbines was approximately 35 years. This compared with expectations of around 28 years for turbines installed up to and including 2007, and 25 years for machines built from 2008. “The service life now depends on turbine size and location and is within 25-40 years, depending on this,” the DEA said.
Italian energy group ERG is pursuing both repowering and lifetime extension measures as it seeks to maintain and build on its domestic portfolio of wind farms. In September, three ERG repowering projects in the southern Italian region of Sicily totalling 143MW were assigned 20-year tariffs in the country’s latest renewable auction. The company aims to add 200MW in net wind capacity through repowering by 2025.
ERG is also refitting 77MW in wind farms in Lacedonia Monteverde in the Campania region and Avigliano in the Basilicata region with more aerodynamic and efficient blades, an upgrade set to be completed in 2023. The business case for that investment comes from a ten-year power purchase agreement (PPA) with Italian telecommunications group Tim. PPAs increasingly providing the financial underpinnings to allow wind farms in Europe to continue running once they exit support mechanisms.
Offshore repowering
While repowering and lifetime extension measures have focused on the more mature onshore wind industry, end-of-lifetime decisions will increasingly also be important for offshore wind.
About 3.5GW of offshore wind capacity globally will reach its designed 20-25-year operational life by 2035, according to a 2021 report from the EU’s Decom Tools project of the Interreg North Sea Region on offshore wind repowering.
While a small number of developers have decommissioned offshore wind farms that reached the end of their lifecycle, Danish company Momentum is widely credited for completing the first partial repowering of an offshore wind farm (right).
In 2018, Momentum replaced the nacelles and blades of the five 20-year-old 550kW WindWorld turbines at its 3.3MW Bockstigen project in Swedish waters with components from used V47-660kW Vestas units, while adding a new control and monitoring system and increasing the site’s nameplate capacity to 3.3MW from 2.75MW. The turbines’ towers, foundations and cabling remained intact.
Danish utility Hofor is now looking to extend the lifetime of its 20MW share of the 40MW Middelgrunden offshore wind farm near Copenhagen, which has been operational since 2001 and has a permit to operate until 2026. Hofor is waiting for a decision from the DEA on extending that permit before proceeding with plans to replace the blades, gearboxes and generators on the turbines. The utility would keep the existing turbine towers and the capacity would remain at 20MW.
Lifetime extensions in the US
Partial repowering, the name commonly applied to lifetime extension measures in the US, continued to be a trend in 2020, according to Lawrence Berkeley National Laboratory’s 2021 annual onshore wind report.
A total of 33 projects involving 1,827 turbines, totalling 3,087MW, were subject to partial repowering in 2020. None of the turbine towers were replaced, but the rotor diameter was increased by an average of 14 metres and the average specific power (W/m2) decreased significantly. The average age of the US wind farms subject to partial repowering in 2020 was just 12 years.
“Partial repowering has been driven by the major growth in rotor diameter in the last five to seven years and represents an attractive value proposition,” explains Mark Bolinger, a research scientist in the electricity markets and policy department at Berkeley Lab. By replacing the rotor and upgrading other components like the gearbox and generator, it is still possible to receive the renewable energy production tax credit (PTC) for another ten years, as long as sufficient funds are spent on the repowering.
Brookfield Renewable Partners highlighted the “attractive repowering opportunity” tied to the PTC when it agreed to purchase the 845MW Shepherds Flat wind farm in the state of Oregon for $700 million at the beginning of 2021 (below). Brookfield expects to increase total generation at the facility by about 400GWh, or around 25%, after upgrades, including increasing the rotor diameter to 127 metres from 100 metres with the installation of new blades.
In 2020, just 343 turbines totalling 120MW were decommissioned in the US and underwent full repowering, being replaced with 50 new turbines with a capacity of 148MW.
Many full repowering wind projects in the US have occurred in California, where the country’s wind industry got started in the 1980s, notes Bolinger.
One of the latest wind farms in California to get a new look was the 57.5MW Scott Haggerty Wind Energy Center (Altamont Winds repowering) , which came online in September. The project is evidence of how repowering can dramatically change the visual impact of a wind farm. It now features 23 GE 2.5MW turbines, whereas before it consisted of 569 tiny 100kW machines.
Preventing servicing problems
As is the case in Europe, some full repowering in the US has been driven in part by concerns about potential difficulties servicing ageing wind farms.
In particular, the bankruptcy of wind manufacturer Clipper in 2012 has helped to spark some repowering deals.
Phoenix Wind Repower, a portfolio investment of alternative asset manager Ares Management Corporation, turned to Vestas with an order to supply its 2.2MW turbines to replace 2.5MW Clipper machines on three Texan wind farms.
The National Renewable Energy Laboratory has estimated that annual US investments for wind repowering — both partial and full — could grow to $25 billion by 2030.
Bolinger expects full repowering will have an increasingly important role to play in the US as wind farms get older, given the ability to leverage off existing transmission infrastructure and interconnection capacity. “Building transmission capacity in the US is very difficult,” he notes.
Increasingly global
While Europe and the US have dominated repowering and lifetime extension investments, how to manage ageing wind assets is increasingly on the agenda elsewhere as well.
Japan’s Electric Power Development, known as J-Power, in September began its fourth repowering project, involving the 24.8MW Nikaho Kogen wind farm in the Akita prefecture. Its J-Wind subsidiary is replacing 15 Vestas 1.65MW turbines running since December 2001 with six Siemens Gamesa 4.3MW machines. The site is expected to begin commercial operations in January 2024.
In China, wind-energy repowering potential is expected to hit 24GW by 2030, according to a forecast from Wood Mackenzie, which stresses the need for policies in the country “to address the feasibility and profitability” of repowering.
Repowering the roughly 10.5GW in sub-megawatt turbines in India with 2MW machines could add 30GW of new capacity in India’s top wind sites, according to a calculation by Kashish Shah, an analyst at the Institute for Energy Economics and Financial Analysis (IEEFA).
A 2021 report by the Global Wind Energy Council (GWEC) India and renewable energy advisory firm MEC+ places India’s potential at nearly 2.9GW for projects with sub-megawatt turbines and more than 15 years of operational life, a figure that is seen rising to nearly 4.5GW around 2030. “Given the challenges around land allocation and cost for new renewables generation, a robust and effective framework for repowering older wind projects at high-resource sites can accelerate India’s renewable energy progress,” the report notes.
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