Published on September 11th, 2009 | by Derek Markham
Electricity from Trees Powers Electronic Circuit
Researchers at the University of Washington have developed a process for tapping into the electrical power of trees, and are successfully running an electronic circuit powered entirely from tree power. The power is in very small voltages, but has now been demonstrated to be usable, and could really change the way we look at trees.
Last year, the team from UW found that plants can generate a voltage of up to 200 millivolts from an electrode in a plant and one in the soil surrounding it. That technology is now being developed for forest sensors. The team wanted to further their tree power research by running a circuit powered solely by trees, and by succeeding, they showed us another unique trait of our leafy friends.
“As far as we know this is the first peer-reviewed paper of someone powering something entirely by sticking electrodes into a tree.” – Babak Parviz, UW associate professor of electrical engineering
One of the co-authors of the study, Carlton Himes, a UW undergraduate student, spent last summer hooking nails to trees and connecting a voltmeter to explore likely sites. Bigleaf maples, which are common on the UW campus, generate a steady voltage of up to a few hundred millivolts, he found. The team next built a device that could run on the available power.
Co-author Brian Otis led the development of a boost converter, which takes a low incoming voltage and stores it to then produce a greater output. The team’s custom boost converter works for inputs of as little as 20 millivolts, lower than any existing such device. The output voltage from the device is 1.1 volts, enough to run low-power sensors.
The circuit built by the UW team is made from tiny parts – 130 nanometers – and consumes just 10 nanowatts of power when operating. That’s not really the range for anything you or I would hook up (no iPod adapters for tree power), but shows some potential for what is doable with the power.
“Normal electronics are not going to run on the types of voltages and currents that we get out of a tree. But the nanoscale is not just in size, but also in the energy and power consumption.” – Parviz
The researchers are quick to point out that tree power is different from the potato or lemon experiment, in which two different metals react with the food, creating an electric potential difference that causes a current to flow. “We specifically didn’t want to confuse this effect with the potato effect, so we used the same metal for both electrodes,” says Parviz
So far, the source of the voltage and the purpose for it in trees hasn’t been established, but some feel that it’s a form of signaling in trees, similar to that which happens in the human body. Researchers are interested in investigating what the tree is doing with the electricity, and compared it to finding a ‘pulse’ for the trees.
The study is being published in the journal Institute of Electrical and Electronics Engineers’ Transactions on Nanotechnology, and was funded in part by the National Science Foundation.