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Tens of thousands of ageing turbine blades around the world are coming to the end of their life cycle, and questions are being raised over exactly what to do with them. In the US alone, about 8,000 will be removed each year between 2020–24. Europe, meanwhile, has about 3,800 coming down annually from 2020–22. This will only increase as most of these blades are coming from turbines built over a decade ago, when installations were less than a fifth of what they are now. Today, there are a number of initiatives under way to address this. Some of these blades are being burned in kilns to create cement or as fuel in power plants, and some original equipment manufacturers (OEMs) are finding innovative ways to reuse them. More needs to be done, however, to prevent turbine blades from ending up in landfill. Looking at future designs, OEMs are searching for more sustainable alternatives by experimenting with more easily recycled fibres, resins and PET foam core. In the case of PET, this is increasingly seen by parts of the industry as a strong, light, recyclable option over incumbent materials. The latest version can help to reduce resin uptake by the foam during composite manufacture, resulting in a lighter blade and lower total cost. Many, however, continue to hold on to the more traditional core materials for a variety of reasons. China, which makes up around 40% of the global wind energy market, initially purchased designs from Germany, the Netherlands and other parts of northern Europe when it started investing in wind energy – designs that typically relied on balsa and PVC. Since its introduction to specific applications in wind, PET has increased its market share, initially at the expense of other foam core types such as PVC, SAN and, most recently, balsa, as the material iterates and improves on its offerings compared with alternatives. “With balsa wood, it’s typically a six-year growth cycle,” explains Ray Lewis, market segment manager of wind energy at Diab, which has caused issues when demand has been prone to fluctuation and rapid spikes in recent years. “If you suddenly want them tomorrow, unless there’s plenty that happens to be available because someone planned them five years ago, you really have a bit of a problem – or, conversely, you build excess stock.” In recent years, political drivers, Covid-19 and the 2020 demand rush have challenged balsa supply. The latter, driven mainly by the looming deadline for Chinese feed-in tariffs at the end of the year, has been most heavily felt in Ecuador, supplier of 75% of the world’s balsa. Local communities were underpaid for their labour and illegal logging became widespread as the nation’s balsa resources were stripped away. As supply got scarcer, the prices doubled or tripled, which, in turn, led to parts of the industry designing blades that have alternative builds requiring different


World Wind Technology / www.worldwind-technology.com


materials, so that they have supply chain flexibility to mitigate risks. Such disruption has occurred before, but as today’s volumes are so much higher, the consequences have had a greater impact. At the same, PET suppliers had been building capacity, so the opportunity to switch had become possible. “OEM’s constantly seek to improve their quality, and a synthetic material is seen as having less variables in volume production,” Lewis says. “With such production globalising, often near to OEM blade hubs, the benefits of localisation on sustainability and cost is clear.” However, to match the strength of balsa, PVC would need to be present in a much higher density, which would be very expensive. PET has similar disadvantages, except the cost is a lot lower. “In the past year or two, some blade designer OEMs have been coming up with the heavier weight PETs to replace balsa,” Lewis says. “Which is a really big paradigm shift – from wood to foam.” Ultimately, lessons need to be learned from the past as we plan for the future. The industry has never been as focused as it is today, whether it’s dealing with old blades, moving from balsa to PET, or manufacturing recycled resins and fibres. However, while the quest for a fully recyclable wind turbine is a worthy one, the real game changer lies in going bigger and in maximising a turbine’s benefits over its lifetime, according to Lewis.


Harness the breeze Rather than going bigger, however, some companies are looking at different ways to alter the design of wind turbines. Some, like the Madrid-based Vortex Bladeless, have come up with designs that completely remove the turbine blades, creating a vertical cylinder that waggles back and forth in the breeze, producing electricity by harnessing the vibrations. Alpha 311, on the other hand, manufactures a small vertical wind turbine that can generate electricity without relying on wind. Instead, the 2m-tall turbine, made from carbon fibre or recycled plastic, is designed to fit on to existing street lights and generate electricity as passing cars displace the air. The company’s CEO and co-founder, Barry Thompson, explains how he and fellow co-founder John Sanderson came up with the idea behind the turbine.


They had started working together on different projects, travelling up and down the UK on motorways, and would often get stuck behind trucks. “You can see the airflow that’s coming off the truck just by the movement of the trees and the foliage that it goes past,” he says. “If you’ve ever stood next to the road as trucks come passing, you feel the impact. [The project] grew from there.” The company’s goal was to simply generate enough electricity at a low cost in order to power a street light. However, rather than proving capable of producing the 150W per day needed to power a street light, the turbines Thompson and Sanderson


8,000


Estimated number of turbine blades that will be removed in the US each year until 2024, as they come to the end of their life cycles.


BloombergNEF


75%


Percentage of the world’s balsa supply that comes from Ecuador.


The Economist 21


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