University of Washington Researchers Develop Electrical Circuit That Runs Off Of Tree Power

September 09, 2009 by Jeff Shepard

Researchers from the University of Washington (UW) are claiming that there is enough power in trees to run an electronic circuit since trees generate power in small but steady quantities. The researchers state that they have successfully ran a custom circuit solely off tree power – which have a voltage of up to a few hundred millivolts (mV).

"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.

The researchers developed a custom boost converter for input voltages of as little as 20mV, an input voltage lower than any existing such device. It produces an output voltage of 1.1V, enough to run low-power sensors.

The UW circuit is built from parts measuring 130 nanometers and it consumes on average of just 10 nanowatts (nW) 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. But the nanoscale is not just in size, but also in the energy and power consumption," Parviz said. "As new generations of technology come online," he added, "I think it’s warranted to look back at what’s doable or what’s not doable in terms of a power source."

Despite using special low-power devices, the boost converter and other electronics would spend most of their time in sleep mode in order to conserve energy, creating a complication in that the system did not wake up. To solve this problem the researchers built a clock that runs continuously on 1nW, about a thousandth the power required to run a wristwatch, and when turned on operates at 350mV, about a quarter the voltage in an AA battery. The low-power clock produces an electrical pulse once every few seconds, allowing a periodic wakeup of the system.

The researchers admit that tree power is unlikely to replace solar power for most applications, 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.