Electrical power from trees

Researchers at the University of Washington (UW) have been able to run an electrical current in small but measurable quantities through trees. According to a research paper from the university, there’s enough power in trees to run small circuits solely off ‘tree power’.

“As far as we know, this is the first peer-reviewed paper of someone powering something entirely by sticking electrodes into a tree,” said UW Associate Professor of electrical engineering, Babak Parviz.

A 2008 study by the Massachusetts Institute of Technology found that plants generate a voltage of up to 200 mV when one electrode is placed in a plant and the other in the surrounding soil. The UW team conducted further research into tree power, connecting a voltmeter across nails inserted into maple trees on the university campus and discovering that they generated a steady voltage of up to a few hundred mV.

The team then built a device that could run on the available power - a boost converter that takes a low incoming voltage and stores it to produce a greater output - working for input voltages of as little as 20 mV and producing an output of 1.1 V. This proved to be enough voltage to run low-power sensors, while consuming just 10 nanowatts of power during operation.

“Normal electronics are not going to run on the types of voltages and currents that we get out of a tree,” Parviz said. “The nano-scale is not just in size, but also in the energy and power consumption. As new generations of technology come online, I think it’s warranted to look back at what’s doable or what’s not, in terms of a power source.”

Tree power is unlikely to replace solar power for most applications, Parviz admits. But the system could provide a low-cost option for powering tree sensors that might be used to detect environmental conditions or forest fires. The electronic output could also be used to gauge a tree’s health.

“It's not exactly established where these voltages come from. But there seems to be some signalling in trees, similar to what happens in the human body but with slower speed,” Parviz said. “I’m interested in applying our results as a way of investigating what the tree is doing. When you go to the doctor, the first thing that they measure is your pulse. We don’t really have something similar for trees.”