Tree Power  

Gizmag has an article on an unusual form of bio-power - generating an electric current from living (not oxidising) trees - Really green power - running an electric circuit from trees.

Researchers at the University of Washington (UW) have taken the term ‘green power’ literally by running an electric circuit from the power generated by trees. Sure, there isn’t much electrical power to harness, but the researchers say it should be enough to run wireless sensors that could be used to detect environmental conditions or forest fires and could also be used to gauge a tree’s health.

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

By hooking nails to trees and connecting a voltmeter, UW undergraduate student Carlton Himes found that big leaf maples generate a steady voltage of up to a few hundred millivolts. The team then developed a boost converter that takes a low incoming voltage and stores it to produce a greater output. The custom boost converter works for input voltages of as little as 20 millivolts and produces an output voltage of 1.1 volts, enough to run low-power sensors.

The circuit the UW team developed is built from parts measuring 130 nanometers and consumes on average just 10 nanowatts of power during operation. Normal electronics obviously aren’t going to run on these types of voltages and currents, so there’s no use packing that big screen TV for your next camping trip, but as new generations of technology come online they will continue to re-evaluate what is doable and not doable in terms of a tree power source.