To address ageing fleets of wind turbines, owners are increasingly facing the choice to either extend the working life of machines or to “repower” existing sites by replacing old turbines with newer, higher capacity technology so prime wind sites continue to be exploited. Industry and policy makers agree repowering is vital to meet renewable energy targets

As wind turbines near the end of their planned operational lives or their output is much reduced in comparison to modern turbines, operators must decide whether to extend the working life of existing machines through judicious component refurbishment or to “repower” existing sites by replacing old turbines with new units. While installing new turbines is generally more costly than reconditioning, the former has the advantage of being more powerful thanks to larger rotors, bigger generators and taller towers capable of reaching stronger winds and generating more revenue. In Europe, repowering involves the complete replacement of turbines, including foundations, the turbine tower, electrical equipment and often the electrical cables. In most cases the old structures are replaced by fewer, bigger turbines, testament to significant increases in turbine sizes over the years. In just five years, the average rated capacity of wind turbines installed on land globally has grown from just under 2 MW in 2014 to 2.4 MW in 2018, as registered by FTI Consulting, a global intelligence business, in its Global Wind Market Update annual report. In the US, repowering generally refers to what Europeans call lifetime extension, or partial repowering, where parts of a turbine, such as the gearbox and blades, are upgraded with newer technology to maximise energy gains. The age of wind turbines is the main reason why the wind industry is repowering in Europe, says Ivan Komusanac of industry association WindEurope. “About 4 GW is more than 20 years old and in the next five years there will be an additional 18 GW of this age,” he says. Europe’s total wind capacity stood at 177.5 GW at the end of 2017. That year, 1 GW of wind farms were repowered, predominantly in Germany, and over the next five years up to 7.3 GW could be repowered, according to WindEurope.

Just the beginning

We are at the very beginning of the repowering journey, says FTI’s Aris Karcanias, who chaired a panel discussion on end-of-life options at the wind industry’s global trade fair in Hamburg, Germany in September 2018. He agrees the wind business recognises it as “an important growth area”. Indeed, Vestas and GE, the world’s biggest turbine manufacturers and operators, have “dedicated groups focusing on repowering within both the sales and the technical units”, he says. “Repowering is not only an important part of Vestas’ business, but of the wind industry in total,” says Jens Kück of Vestas in Germany. While Europe’s old turbines are the main reason for repowering on the continent, there are a multitude of other considerations, technological, operational, financial and regulatory that influence decisions on the issue. These can include the end of planning permits or land leases. “It is extremely complex,” says Komusanac of WindEurope. “Every situation has its own story.” There is wide variation in planning and permitting rules between European countries, but also between different regions and even municipalities. There are currently no standard procedures across Europe when a wind farm owner wants to repower. In some countries, for example, stricter environmental impact assessments may be required.

Windy sites taken

“One of the biggest difficulties we have today is that a lot of the permitting rules are not fit for addressing historical projects which often have prime wind sites,” says Karcanias. Indeed, all the best wind sites in Europe have already been exploited in Germany, Denmark, Spain and Italy and companies don’t want to risk losing access to them. “There is a serious need to avoid any delay in repowering these projects and to change the way we permit new technologies,” adds Karcanias. To date six EU member states have included definitions of repowering in their national legislation, while only one country, Italy, has put in place a “concrete incentive for lifetime extension projects”, according to a 2017 WindEurope report. A pro-active approach to repowering wind farms is “critical to deliver on the EU’s objective to meet a 50% share of electricity generated by renewables by 2030”, it says, in order to prevent key, known wind sites ceasing to produce renewable electricity. Karcanias is critical of the impact of regulatory delays in repowering. If opportunities are missed “we won’t be utilising all of the benefits of the historical feed-in tariffs that helped pay for this technical wind evolution”, he says.

Regulatory push

To smooth the way for repowering in Europe, WindEurope and representatives of the industry at a national level, such as the German Wind Energy Association, are calling for simplified and speeded up permitting procedures for repowering projects. WindEurope welcomes the recently revised European renewable energy legislation, which calls on member states to facilitate the repowering of existing renewable energy plants by ensuring a “simplified and swift permit granting process” that should not exceed one year. Political agreement on the new legislation was reached in June 2018 and is expected to be formally adopted later this year, giving countries until June 2021 to transpose the measures into national law.

US tax credits drive turbine upgrades

Across the Atlantic the wind fleet is younger than in Europe, with 83% of the US’s installed wind turbine capacity less than 13 years old, according to the Energy Information Administration, the statistical and analytical agency of the US Department of Energy. Some European-style repowering has occurred in California, where many turbines were installed at high wind sites prior to 1990. Partial repowering is, however, most common in the country as a whole, driven not by the age of the fleet, but by the production tax credit (PTC) for wind energy offered by the US government, and the ability of newer technology to yield more energy. In 2017, 2136 MW of partial repowering was completed out of a total wind capacity of 89,000 MW, according to the American Wind Energy Association (AWEA). “The US market has very clear and evident repowering potential,” says Karcanias. This is based on the availability of a PTC extension when at least 80% of the value of the turbine is upgraded. “It won’t necessarily make sense to replace the whole unit in order to qualify for the PTC so in some cases they cut off the turbine’s head and replace it with a new nacelle [housing all the drivetrain components] and new blades.” The US tax credit is, however, being reduced by 20% in 2019 and is due to end in 2020. The change may reduce the industry’s appetite for such upgrades.

Second hand market

One option that can go hand-in-hand with repowering is the sale of old wind turbines to give them a second life elsewhere. Previously when old turbines were taken down they were scrapped. “They were simply completely worn out and it didn’t make sense to reinstall them,” says Glen Aagesen of Fairwind, a global provider of one-stop solutions for onshore and offshore wind turbines. “The tendency now is to renovate and sell them on as second hand turbines. The graphic is changing from scrapping to refurbishing.” The second-hand market is, however, “not as buoyant as some people had hoped it would be”, says Karcanias of FTI Consulting. “This is due in part to the significant reduction in the cost of new turbines and the fact that new turbines are likely to have a longer lifetime.” Aagesen agrees the market is “immature”. He adds: “There are a lot of lessons still to be learned, but a lot of companies are looking into it.” The main sales for old turbines are from mature markets, such as Germany, to emerging markets in Eastern Europe, South Africa, Russia, Latvia and Poland. “But sometimes they are also sold to other mature markets like Sweden where private investors are buying them,” says Aagesen. WindEurope’s Komusanac says the association does not track the second hand market although he knows of examples of second hand turbines being sold from Denmark to Cuba, Italy and Ireland. A new onshore turbine, excluding construction work, costs around $700 a kilowatt of capacity, according to the International Renewable Energy Agency. Second hand turbines can therefore make sense for developing countries if they can be sold at a much lower price, explains Komusanac, although newer turbines are better and more efficient because of the experience gained from older turbines. Further, the process of dismantling turbines for resale is onerous. This will not only impact the potential growth of the second hand market, but also the players involved. “Now when the original equipment manufacturers take down turbines [for refurbishing] they need to document everything with regard to quality, health and safety, for example, like they do during installation,” says Aagesen. This will remove a lot of the smaller contractors from the market, he comments, mirroring the trend in the installation market over the last ten to 15 years. “Where previously you had what we called the wild west days where anyone could install a turbine, today it is very complex, with complex machinery, health and safety, and training.” This has led to the merging of a lot of smaller companies so you see fewer, bigger companies, says Aagesen. “In the next two to five years you will see the same tendency in decommissioning and repowering. There’s no doubt about that.”

Writer: Iva Pocock