Mimicking Nature, Minimizing Turbulence

Photograph by William R. Curtsinger, National Geographic

A school of snappers arranges itself to reduce drag and increase efficiency, much as a flock of geese flies in a “V”.

“There’s a lot of information in the literature as to what the optimal fish school should look like,” said CalTech bioengineering professor John Dabiri. So in order to design a better arrangement of wind turbines, his team looked to fish.

Arranging vertical turbines in a school-of-fish pattern allows them to be placed closer together without the turbines’ wakes interfering. “We wanted to achieve something similar [to fish schools], where instead of minimizing energy consumed we wanted to maximize energy generated,” said Dabiri, of California Institute of Technology’s Center for Bioinspired Engineering. ┬áThe goal, he said, is to increase the amount of wind energy that can be generated in the same amount of space, and so far, the experiments have produced a stunning ten-fold gain in efficiency.

Photograph courtesy John O. Dabiri, Caltech

Because the turbines are vertical and shorter than typical propeller-style turbines, they’re also quieter and safer for migratory birds than the typical turbines, Dabiri said.

But as seen in the energy applications of bull kelp and termite mounds, nature doesn’t necessarily hold all the answers. A lively debate on the limits of biomimicry was touched off when 13-year-old Aidan Dwyer last year won a Young Naturalist Award from New York’s American Museum of Natural History for a bio-inspired array of solar panels: instead of arranging them in rows, he built a “solar tree,” with panels arranged like leaves on branches.

Bloggers and scientists took Dwyer to task because, when he measured the effectiveness of the panels, he measured voltage instead of power (a combination of voltage and current). In fact, arranging panels to mimic a tree isn’t the most efficient layout, because trees aren’t the most efficient collectors of sunlight, said Jan Kleissl, an environmental engineer at University of California, San Diego, in an email. “Trees have to combat weight and wind loading. If trees used a steady, continuous surface that was always oriented perfectly towards the sun, the force of strong winds would topple the tree . . . Evolution has to make great trade-offs in supporting life.”

The fact that nature can’t always serve as a cheat sheet for humans is the “unpopular yet true story,” Kleissl added. “Human ‘evolution’ left natural evolution in the dust during industrialization.”

Still, biomimicry advocates believe that nature offers enough lessons about storing and using energy that civilization needs to try to apply these ideas that have evolved over eons, combining them with the human ingenuity of today.

by Rachel Kaufman

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