A Wind Turbine Inspired by the Palm Tree
Folding Rotor Concept Could Enable Offshore Turbines with Six Times More Power
Imagine a wind turbine with blades longer than two football fields that curve and fold in the wind like a palm tree’s fronds. According to a technical brief by EPRI’s innovation scouts, the application of this concept—known as the segmented ultralight morphing rotor—has the potential to increase a turbine’s power output by six times and cut in half its levelized cost of electricity.
The size of conventional upwind turbines is constrained by blade mass. Blades must be stiff so that they don’t bend back and strike the turbine. These stiff, heavy, long, and massive blades place stress on the turbine and require expensive towers. Their manufacturing and transportation costs also add up. The largest commercially viable machines are rated at 8 megawatts and have 260-foot blades.
With funding from the U.S. Department of Energy, a team led by the University of Virginia is designing a downwind turbine with an ultralight, segmented rotor that flexes and “morphs” in the wind. Blades are open at low wind speeds to catch as much wind as possible. As wind speeds increase, the blades curve inward to align the load and optimize energy production. In extreme winds, the blades fold together, avoiding rotor damage and reducing stress on the tower. The design could potentially enable 50-megawatt turbines with 650-foot blade lengths; less massive towers and foundations; and lower manufacturing, transportation, and assembly costs. It could also facilitate offshore development despite hurricanes and other severe weather with wind speeds greater than 200 miles per hour.
The concept has been simulated, and in 2019 the University of Virginia team plans to test a prototype one-tenth of the size anticipated for a 50-megawatt turbine. Given the significant R&D needed to optimize the blade, rotor, generator, tower, and other components, commercial deployment of 15- to 25-megawatt turbines may be about a decade away.
Artwork by Kirk Anderson