While high-tech developers work towards efficient wind farms and solar collectors, heat pumps, and storage cells, some innovators are using the structures of nature for their inspiration.
Recognizing that nature is the most effective converter of solar input to electricity, a number of efforts have focused on using nature’s architecture as a model to maximize the solar-collecting abilities of human-made solar technology. Where commercially-available solar cells have a maximum efficiency rate of only about 20%, it is hoped that using nature’s strategy for solar energy collection will yield more impressive results.
One of the first efforts in this direction was a science-fair project developed by a thirteen-year-old student, Aiden Dwyer, who observed that oak trees deploy their leaves in a Fibonacci pattern that allows maximum exposure of leaf surfaces to the sun. His project yielded 50% greater efficiency than traditional solar panels. Although critics have questioned Dwyer’s specific conclusions, they have also conceded that the technology offers some clear advantages over traditional solar collection techniques.
Another promising lead for solar collection development is the use of fractal patterns to maximize leaf surface exposure. Fractal patterns are patterns that exhibit repeating patterns at every scale, so that at any scale, the pattern of leaf distribution is the same. This pattern is also known as expanding symmetry – even as the scale changes, the distribution scales up or down, but does not change.
Fractal patterns occur naturally in leaf distribution among trees and provide maximum exposure of the photosynthetic leaf surface – and the patterns are repeated at any scale. Trees are able to absorb the maximum amount of sunlight because of the fractal pattern of leaves that maximizes surface exposure.
In an ambitious study headed by Professor Frank Osterloh of UC Davis, his team developed a set of microscopic, intricate “tree-structures” grown from silver nitrate, which grows fractals after applying fluorine-doped tin oxide to silver salt. This treatment causes an electrochemical reaction in which the silver nitrate grows into a miniature “tree,” with “branches” one-fiftieth the width of a human hair. These tiny branches are themselves branched, creating a microscopic tree-like structure with a proportionally large canopy that is ideally arranged to collect solar energy. The fractals were coated with light-absorbing polymers. When photons come into contact with the polymers, short-lived positively-charged electrons create an electric potential.
Finally, French entrepreneur Jérôme Michaud-Larivière has built on these models by creating leaf-like collectors distributed mathematically on a tree in imitation of natural growth. These collectors don’t need a great deal of wind to operate, able to be activated by a light breeze. When activated, the S-shaped “aeroleaves,” as Michaud-Larivière calls them, rotate at sufficient speed to convert wind to electrical impulses.
While the efficiency of this technology needs to be improved to compete with these other nature-based technologies, developers are optimistic about this and other approaches that use nature as a model to produce sustainable energy.