Tree powers electronic circuit

You’ve heard about flower power. What about tree power? It turns out that it’s there, in small but measurable quantities. There’s enough power in trees for University of Washington researchers to run an electronic circuit, according to results to be published in an upcoming issue of the Institute of Electrical and Electronics Engineers’ Transactions on Nanotechnology.

“As far as we know this is the first peer-reviewed paper of someone powering something entirely by sticking electrodes into a tree,” said co-author Babak Parviz, a UW associate professor of electrical engineering.
Electrical engineers Babak Parviz and Brian Otis and undergraduate student Carlton Himes built a circuit that runs entirely off tree power

Electrical engineers Babak Parviz and Brian Otis and undergraduate student Carlton Himes (r-l) built a circuit that runs entirely off tree power.

A study last year from the Massachusetts Institute of Technology found that plants generate a voltage of up to 200 millivolts when one electrode is placed in a plant and the other in the surrounding soil. Those researchers have since started a company developing forest sensors that exploit this new power source.
The UW team sought to further academic research in the field of tree power by building circuits to run off that energy. They successfully ran a circuit solely off tree power for the first time.

Co-author Carlton Himes, a UW undergraduate student, spent last summer exploring likely sites. Hooking nails to trees and connecting a voltmeter, he found that bigleaf maples, common on the UW campus, generate a steady voltage of up to a few hundred millivolts.

The UW team next built a device that could run on the available power. Co-author Brian Otis, a UW assistant professor of electrical engineering, led the development of a boost converter, a device that takes a low incoming voltage and stores it to produce a greater output. His team’s custom boost converter works for input voltages of as little as 20 millivolts (a millivolt is one-thousandth of a volt), an input voltage lower than any existing such device. It produces an output voltage of 1.1 volts, enough to run low-power sensors.
The UW circuit is built from parts measuring 130 nanometers and it consumes on average just 10 nanowatts of power during operation (a nanowatt is one billionth of a watt).

“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 said.

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