Insect-Inspired Turbine Blades Could Radicalize Renewable Wind Power

Flexible blade design based on dragonflies could fundamentally change how we harvest wind energy.

Published on 2/17/2017 at 1:53 PM

It's just like grandma used to say: When designing efficient wind-turbine prototypes, be sure to employ biomimetic synthetics inspired by dragonfly wings. Yes, grandma was a singular woman....

Encouraging new research out of Europe suggests that bio-inspired turbine blades - based largely on the flexible wings of insects - can improve wind energy production by up to 35 percent. That's a very big number in this context, and the research may well trigger a fundamental change in how we harvest wind power.

Published this week in the Proceedings of the Royal Society A: Mathematical and Physical Sciences, the research details a series of experiments in which flexible turbine blades were matched against traditional rigid blades in head-to-head tests.

The flexible blades were designed to mimic the motion of insect wings and, to a lesser extent, certain plant leaves. Due to a particular kind of structural flexibility, insect wings are able to redirect airflow in a manner that significantly increases the power they need for lift. For insects like the dragonfly, the redirected wind makes it much easier to fly, because they're not expending as much energy.

But it turns out that the same principles, when applied to the design of a fixed wind turbine, increase the ultimate power output the device. That's because flexible turbine blades can adjust to the pitch angle of incoming winds. By going with the flow, quite literally, flexible turbines can optimize the amount of torque applied to the generator.

To get hard numbers for the phenomenon, scientists built three small turbine prototypes, each with a different configuration of blade flexibility. One model used completely rigid blades, another was highly flexible, and the third was somewhere in between.

Subsequent experiments showed that the highly flexible blade was too wobbly to produce proper torque, and in fact didn't generate as much power as the traditional rigid blade. But the moderately flexible blade consistently outperformed the rigid blade, creating up to 35 percent more power.

What's more, the flexible blades were able to function in a much wider range of wind conditions, generating power in instances when the rigid blades underperformed. Long-term testing also suggested that the flexible blades were much less likely to jam or break under severe wind conditions.

In the study abstract, lead author Vincent Cognet of Paris-Sorbonne University said that traditional turbines are inherently limited because they're designed to operate within a narrow zone centered around their optimal working point. The new flexible blade approach would not only produce more efficient wind turbines, it could allow for more wind farms in more locations.

"This limitation prevents the use of sites with variable wind to harvest energy, involving significant energetic and economic losses," Cognet said. "Here, we present a new type of bioinspired wind turbine using elastic blades, which passively deform through the air loading and centrifugal effects."

If you really want to dig into the specifics, the full paper is available online at the The Royal Society website, along with some helpful graphs on the relevant elasticity mechanisms and aerodymanic lift coefficients. Gosh, grandma would have loved this stuff....

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