HSE


By 2030, experts predict that new wind towers will reach average heights of 115m, even as some companies have plans for 199m designs and beyond.


awkwardly transport mammoth towers to their foundations. Light and flexible, wood suffers no such limitations, allowing engineers to slot tower sections together on site, potentially making building towers safer and cheaper than ever before – a particular boon given towers are only growing in size. By 2030, experts predict that the average new tower will reach a height of 115m, while Vestas recently unveiled plans for a monster 199m design. Yet, if the theoretical advantages of wooden towers are secure, how are they faring in practice? Once again, Dölerud is a good person to ask here. In 2020, after all, he and his Modvion colleagues successfully got a 30m tower working on the Swedish island of Björkö. That’s literally shadowed by another project, this time a 100m machine for Varberg Energi. And, as Dölerud stresses, these varied tests are already proving their worth. For one thing, they’re helping the team clarify their decision to promote what he calls “common interfaces” with more traditional turbine designs – for instance, in the way the tower is connected to the foundation. At the same time, Dölerud continues, these real- world applications are helping Modvion understand how wooden towers function as so-called ‘dynamically loaded’ structures – in other words, structures whose forces change over time. There may be areas to work through as well. As a natural material, for example, Hall notes that wood is isotropic. Unlike steel, which is strong whatever way you pull it, this means timber has particular weaknesses from particular directions. To explain what he means, the professor gives the example of a tree. “You pull a branch one way versus trying to pull it another – it’s going to be different.” To be fair, Hall says that laminating wood from different directions can overcome these difficulties, which is exactly what Modvion is doing. Nor does


World Wind Technology / www.worldwind-technology.com


this process of strengthening really increase the overall weight of a wooden turbine. As Modvion reports, their machines are still about 30% lighter than conventional towers.


Steel yourselves With all this in mind, it’s tempting to imagine that wooden turbines are destined to dominate wind over the years ahead. If nothing else, this is reflected in the broad direction of travel. Modvion, for its part, has ambitions to become the leading supplier of wind turbine towers by 2030 – and its recent deal with RES is surely a good start. Beyond that, Voodin is rushing ahead too, installing its first 20m blades on a test turbine in central Germany at the end of 2022. “I don’t see any obstacle for this to become very competitive compared to steel-based or concrete- based solutions,” is how Dölerud summarises the situation, adding that especially as towers continue to grow “we will see a strong drive towards timber- based power solutions in the future”. Hall, for his part, is fairly optimistic too. If necessity is the mother of invention, he suggests that a shortage of cheap steel could be a “big driver” towards a timber-built tomorrow. Between sanctions targeting Russian mining, and the persistent struggle of mills to ramp up production post-Covid, this is certainly a possibility. As a recent report by S&P Global notes, moreover, electrical steel alone could be facing a 927,000t shortfall by the end of the decade. All the same, Hall is reluctant to discount traditional turbine manufacturing entirely. As he says, steel remains a “formidable opponent” to companies like Modvion, noting that in terms of the robustness of the material alone, wood could struggle to out-muscle steel entirely. The future may be wooden, in short, but William Kamkwamba is perhaps destined to be an outlier a little longer. ●


100%


The jump in the cost of steel in the 12 months following August 2020 due to challenges around the


Covid-19 pandemic. International Energy Agency


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Modvion


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