By Amaya Paleja
As kids, you might have spent many afternoons, under a huge tree, enjoying its shade. In a tropical country like India, trees are a welcome sight in the month of May, when the sun is blazing in the sky and the shade offered by them is a hundred thousand times better than artificial cooling of the air conditioning units. But never in our dream would we have thought that the rustling of the tiny leaves of the trees could one day make electricity for us.Because that requires a Hendersonian moment! (just in a bit).
This brilliant idea has come from the lab of a biophysicist at Iowa State University, Dr. Michael McCloskey, whose work at the University largely involves the study of membrane transport in algae and adult born neurons but also has a background in plant sciences. It was his colleague in the department of genetics, Dr. Eric Henderson who first came up with this plan of harvesting energy from leaves as he wondered how much kinetic energy was being generated when winds blow across leaves. The researchers, then spent the next year and a half seeking a grant from various organizations to take the idea further and after a couple of failures managed to convince the National Science Foundation to fund their idea. Researchers were also inspired by the fact that many cell phone towers in the United States (see Robert Voit’s beautiful pictures here) were being artificially draped for the singular purpose of aesthetics.
In this study, Dr. McCloskey and his team created a prototype of a plant and used piezoelectric materials inside the artificially created leaves to harness electrical energy every time the “leaves” were swayed by the wind. Piezoelectric materials respond to mechanical stress by generating a small charge and have been known to man since the late 1800s. While the prototype (picture below) does not even remotely look like a tree, the researchers are positive that they have taken the a step in the right direction and needs a lot of work before we see a practical outcome.
Prototype of tree whose leaves generate electricity | Image credit: Christopher GannonTraditional wind turbines require winds to blow at least at the speeds of 7 miles per hour (mph) to generate electricity. On the other hand, using piezoelectric material, electricity can be harnessed from winds that are far lesser speeds. Add to it the advantage of having thousands of leaves on a single tree, the harnessing outcome increases multi fold.
One could argue that not all leaves on a given tree would flutter at the same speed and pattern, yet the average capability of a tree made of such “leaves” would still be pretty good. According to estimates by the researchers, a regular cottonwood tree with about 50,000 leaves could harness a maximum of 80W of energy, which is sufficient to carry out charging batteries of smaller appliances in off-grid set ups. (This is still lesser than commercially available AeroLeaf, pictured below,) The massive advantage of such a setup would be easy installation of such trees in densely populated areas as well as the reduction in noise as compared to traditional wind mills.
AeroLeaf are commerically available artificial trees that can harness energy from the wind | Photo credit: IISD.Their research findings published in PLoS One have shown that using the currently available technology the prototype could not deliver the energy efficiency expected out of a commercial product. New Wind’s AeroLeaf biomimetic wind turbine that has a maximum power generation capacity of 100W has already reached the market and has installations in urban landscapes of Germany, Switzerland and France. Dr. Henderson, admits that piezoelectric materials were the obvious place to start because of their ready availability and it was Dr. McCloskey’s ingenuity that allowed them to conclude that energy harvested was not at par to current industry standards.
When inquired over email regarding using actual trees to harness energy rather than artificial ones, Dr. McCloskey was quite positive and strongly believes in conserving trees and fitting them with devices that could harness energy for us rather than building artificial and aesthetic ones. In fact, his previous grant proposals included this concept but were rejected. Dr. Henderson, co-author of the study, adds that funding is a highly subjective process and he cannot really decipher why a study with the same basic science would be treated differently at different times. Something for funding agencies to look into!
But how did professors in biophysics work on project of harnessing wind energy? Dr. Henderson says that he does not recognize disciplinary boundaries but thinks of himself as an old school scientist, who is a problem solver and not a micromanager.
The researchers are now eager to work on a new method with a radically different piezo electric material that can deliver better efficiency to the extent of amplifying their current outputs by 100,000 fold and which will enable them to make a practical device. Hopefully, this device will be fitted on normal trees that will not only clean the air for us but also generate electricity. Probably then, people would think twice before cutting a tree!
Ameya Paleja is a Molecular Biologist by day and a blogger by night. He also likes to write about Genetics, Microbes and Future. He supports development of ‘greener’ sources of energy and blindly believes that solar power is the answer to all our energy needs.
This article is originally published on Coffee Table Science.
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