Wooden Wind Turbine Towers Reach New Heights

Wood might seem like a construction material from a bygone era, but Swedish startup Modvion is putting it to a very modern use. The Gothenburg-based company is using engineered wood to build wind turbine towers, and it recently received design certification for the tallest one to date: 119 meters, matching the height of most onshore wind turbines in operation. The company’s tower can support a 6.4-megawatt turbine.

Wood has experienced a renaissance in recent years, with growing recognition of its potential as a strong, lightweight, and low-emission structural material. Engineered wood products are created by binding sawdust, wood fibers, or even entire planks together with adhesive. They can be considerably stronger than standard timber and have been used to construct high-rise buildings in Australia, Canada, Norway, and the United States.

The material is particularly promising for building turbine towers because of its great strength-to-weight ratio, says Modvion’s senior development engineer Erik Dölerud. It also enables the manufacture of smaller modules that can be assembled on site, reducing transport challenges, he says. The company constructed a 103-meter tower in Skara, Sweden, in 2023. Its new 119-meter design received sign-off from the independent certification and testing specialists TÜV SÜD, in Munich last month.

“Wood is the original high-performance construction material and in the past 100 years I think it’s been underutilized,” says Dölerud. “When you think about it, a tree has evolved through millions of years to carry load and survive wind so it’s not difficult to envision that it’s a pretty suitable material for this type of application.”

Engineered Wood: The Future of Wind Turbine Towers?

The company builds its towers out of laminated veneer lumber (LVL) which is made by adhering together many thin layers of wood to create a structural material that’s stronger than timber. Slicing the timber apart and bonding it back together evenly distributes wood’s localized weaknesses, like knots and grain differences, says Dölerud. The result is a material that is stronger than steel for a given weight.

Modvion assembles its towers out of a series of curved wooden modules roughly 15 meters long. The base of each tower is comprised of six of these modules and the top sections use four. Manufacturing these modules involves laminating several large boards of LVL and then pressing them over a large cylinder to create their curved shape.

To create these curved shapes the company had to engineer bespoke LVL boards with a particular distribution of grain directions that makes them bendable and able to lock together during the bending process to create a stiff structure that holds its shape. Once all the tower’s modules are built, they are transported to the site and adhered with glue to create tubelike sections that are then stacked on top of each other using a crane.

One of the biggest appeals of the approach is that constructing the towers from wood produces 90 percent fewer lifetime carbon emissions than building them with steel, according to a life-cycle assessment by the Research Institutes of Sweden (RISE). Being able to transport the tower in parts has significant benefits over conventional wind turbine towers, which are normally made from long sections of tubular steel that are difficult to maneuver down narrow, winding roads. Modular steel towers do exist but they require huge numbers of bolts to assemble them that have to be painstakingly inspected and adjusted at regular intervals and can be prone to failures, Dölerud says. Inspection of Modvion’s joints is much faster and simpler, he says.

Modvion built a 103-meter wind turbine tower out of engineered wood, and has designed a 119-meter version that can support a 6.4-megawatt turbine. Modvion

Sustainable Construction with Laminated Veneer Lumber

Proving the benefits of the approach can be challenging though, because international technical standards for turbine towers don’t account for the use of wood as a structural material. This prompted Modvion to enlist TÜV SÜD to provide an independent evaluation of its latest tower design. The evaluation involved combing through stress-testing data collected by Modvion on all of its components, in collaboration with RISE.

Modvion’s 119-meter tower is designed to support a 6.4-MW turbine made by Danish company Vestas. This was challenging due to the lack of regulations covering wood and glue when used as structural materials, says Stephan Mayer, TÜV SÜD’s head of the tower and foundation group within the wind-energy department.

At 119 meters, the tower would be directly competing with cheap tubular steel towers exported from China, notes Mayer, which might be challenging as Modvion has yet to set up a serial production process. Dölerud acknowledges that competing with tubular steel on cost will be tough. But for towers above 150 meters, the industry primarily relies on hybrid towers combining a concrete base with steel upper sections, he says. These are significantly more expensive than tubular steel towers and require large amounts of material to build, says Dölerud. He expects Modvion to be cost-competitive with these towers.

The company won’t actually build the 119-meter tower, which was designed only to prove that Modvion could support the Vestas’s 6.4-MW turbine, and is now shifting focus to designing a 160- to 170-meter tower which it expects to be finalized by 2027. “But who knows what happens in the future?” Dölerud adds. “Maybe we are able to optimize a lot this new technology when we are in full-scale production, and then we can start to try to compete in the tubular steel market as well. But this is not our primary focus at this stage.”