Trees as Power Sources

A Massachusetts Institute of Technology study found plants can generate up to 200 millivolts between an electrode in the plant and one in the surrounding soil.
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Researchers at the University of Washington have developed a custom circuit that can be powered from the limited power available from trees.

A Massachusetts Institute of Technology study found plants can generate up to 200 millivolts between an electrode in the plant and one in the surrounding soil. The UW team found that big leaf maples generate a steady voltage up to a few hundred millivolts. The UW circuit consists of a boost converter that steps up voltages as low as 20 millivolts to 1.1 volts It consumes only 10 nanowatts of power during operation. To further reduce energy consumption a clock that runs continuously on only 1 nanowatt is used to turn on the system once every few seconds.

The low power circuits could be useful for powering sensors that could, as an example, provide early notification of forest fires. This, of course, will require developing transmitters than will work with the small amount of power available from the tree.

"It's not exactly established where these voltages come from," said Babak Parviz, University of Washington associate professor of electrical engineering. "But there seems to be some signaling in trees, similar to what happens in the human body but with slower speed. 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."

In case you are wondering, this is not the same as the "potato battery" effect where dissimilar metal electrodes are used to produce voltage. The electrodes in this experiment used the same metal. Read Electrical circuit runs entirely off power in trees for more information.