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The world's wind turbines are growing. From the early models in the 1990s of less than 1 megawatt, turbines are now being developed with a capacity of 16 megawatts or more, with blades longer than football pitches, supported by towers rising more than 100 metres into the air.
Taller towers can harvest stronger and more reliable winds, making them more efficient and cost effective. For the biggest turbines a single rotation of its massive blades can power a home for two days. But, building bigger also has its problems.
Other parts of the supply chain need to adapt to the huge increases in size and weight. A report from consultants Wood Mackenzie this year said that about half of the world's installation vessels are set to retire because they are not designed to cope with the newer turbine models, with about $13bn of investment needed for replacements.
Another concern is the massive turbines' environmental footprint. Turbines are usually constructed from steel, the blades from epoxy or fibreglass reinforced polyester. Those steel towers are energy intensive to produce, while decommissioned blades will often end up in landfill.
But one option emerging which may temper that environmental impact are wooden turbines. Swedish start-up Modvion has built a 30-metre tower in Sweden using sections of laminated wood. And work is currently under way on a 105 metre tall turbine. The aim is to ultimately build towers of up to 150 metres.
Modvion claims the wood is stronger per weight than steel and more cost effective. The towers can be slotted together on site, which means that they can be transported on standard roads without lengthy permit procedures. According to Swedish research institute RISE, using a wooden tower reduces emissions by 90 per cent across its lifetime compared to a steel tower of the same height and load.
Meanwhile, German start-up Voodin Blade Technology is building its first wooden blades. These are 20 metres long, but work is also under way on an 80-metre long blade.
Given their relative newness, the biggest obstacle to wooden turbines' uptake may be uncertainty about their performance in the long term. But there are signs of willingness in the market. For example, UK-based company Renewable Energy Systems has signed a letter of intent to use around 20 of Modvion's wooden towers a year from 2026 to 2036.
And with the wind turbine market expected to grow significantly this decade, if there are shortages in materials such as steel, wooden turbines could at least play the role of complementing traditional turbine construction.
