Biomimicry for wind and solar energy harvesting
Japan’s Research in Aerospace Engineering Department has been conducting research into “flap-type flying robots” and has conducted various experiments and simulations in this area. As part of his research he filmed a model dragonfly wing moving through a tank of water with added aluminium powder – as air flow behaves the same way as water. He found that when air passes by a dragonfly’s wings, tiny peaks on their surface create a series of swirling vortices.
Kobata studied how the vortices affected the dragonfly’s aerodynamics and how the dragonfly wing stayed the same even at varying low current speeds, but its aerodynamic performance fell drastically as either water speed or the wing’s size increased. Using this information Obata and his colleagues developed a low-cost model of a micro wind turbine whose 25-centimetre-long paper blades incorporated bumps like a dragonfly’s wing.
Meanwhile, a Tel Aviv University team has demonstrated how the Oriental hornet uses energy from the sun and converts it into electric power using the brown and yellow parts of its body which act as a photovoltaic cell.
Physicist Prof. David Bergman of Tel Aviv University’s School of Physics and Astronomy says “The interesting thing here is that a living biological creature does a thing like that. The hornet may have discovered things we do not yet know.” Research into the biological processes that turn a hornet’s abdomen into solar cells was conducted by Professor Bergman together with the late Prof. Jacob Ishay of the university’s Sackler Faculty of Medicine, and Prof. Bergman’s doctoral candidate Marian Plotkin.
It has been observed by entomologists that Oriental wasps, unlike other wasps and bees, are active in the afternoon when the sun is high, and not in the morning when the sun is just rising, and the hornet is more active as the sun’s intensity increases.
The Tel Aviv University team studied weather conditions like temperature, humidity and solar radiation to determine if and how these factors also affected the hornet’s behaviour, but found that UVB radiation alone was responsible for the change.
In the course of their research, the Tel Aviv University team also found that structures in the brown part of the hornet trap the solar light and beam it into lower layers studded with rod-like structures that keep the energy bouncing between them. The yellow part gets its colour from a pigment called xanthopterin that turns light into electrical energy. “These structures are very complicated,” Plotkin explained. “To build something similar would be very expensive and complicated, but the insects do it naturally.”
The researchers also learned that the hornet has a well-developed heat pump system in its body which keeps it cooler than the outside temperature while it is active in the sun.
The research team plans to discover if this biomimicry can give clues to novel renewable energy solutions.
Sources: Nippon Bunri University & American Friends of Tel Aviv University
For more read : Energy Harvesting and Storage for Electronic Devices 2010-2020 
and attend Energy Harvesting & Storage and Wireless Networks & RTLS Europe 2011
