The voltage potential is small, but its unflinching continuity means it could be reliably used to trickle-charge a battery or capacitor. This, in turn, can be used to power a wireless sensor node four times a day to transmit data. By implementing a mesh network among the nodes installed on trees, the researchers plan to pass along sensor data from node to node until it reaches a regional weather station. The station would then relay separate sensor readings from individual trees to a central fire-prediction computer.
MIT recently spunoff a company to capitalize on its discoveries about tree power, called Voltree Power (Canton, Mass.) where Mershin is scientific advisor. MIT senior Christopher Love is the vice president for R&D at Voltree. Together, Mershin, Love, Shuguang Zhang, director of MIT's Center for Biomedical Engineering, have been able to boost the original millivolt-scale potential to over 1 volt, enough to trickle-charge a battery, power a radio and broadcast the output from sensors to a mesh network.
"Voltree has perfected its technique with a proprietary selection of metals for electrodes and an underground electronics box with a spike in it that penetrates the tree at its roots," said Mershin.
A second electrode in surrounding soil supplies a ground for the wireless sensor node electronics. An antenna wire snakes up the tree alongside a wiring harness, connecting the tree-mounted sensor to the underground electronics.
Field testing of the tree-powered wireless sensor network is currently being readied on 10 acres designated by the U.S. Forest Service for spring 2009 trials.
Funding for the tree power research was provided by MagCap Engineering and MIT's Undergraduate Research Opportunities Program.