The sensor’s design is based on research conducted by Massachusetts Institute of Technology students into how trees generate electricity and ways to harvest it. According to an article by the university’s news office, a tree generates a trickle of electricity — around 100 to 200 millivolts — that can fill a rechargeable battery over time. The battery provides enough energy to allow the sensor to send its data back to the weather station four times a day or immediately if there’s a fire.
Original sensor designs used embedded wireless transmitters to relay the signals from sensor to sensor until it reached a weather station that would then beam the data back to a Forest Service station in Boise, Idaho. Future designs may use ultra-high radio frequency radio transmissions, according to Stella Karavas, CEO of Voltree Power.
Field Test
In May the U.S. Forest Service facilitated a test of the bio-energy harvesting technology in Boise National Forest in which the company’s engineers deployed the sensors as far as a quarter mile from a RAWS.“The idea of being able to have the capability with sensors out there rather than [in] just one spot, which is basically where you set up the weather station, and actually have them powered by vegetation was pretty intriguing to us as an agency,” said Victoria Henderson, branch chief of equipment and chemicals for the U.S. Forest Service’s Fire and Aviation Management unit.
Having the sensors deployed around the weather stations will give the Forest Service in Boise more detailed information on characteristics of wildland fires and prescribed burns. "So you’re able to capture that and be able to refine your tactics or deal with sudden spikes in temperature,” Henderson said. Deploying the sensors could also be cheaper than having to set up more weather stations.
The test in May was conducted in a controlled area of Boise National Forest. Voltree Power engineers deployed five sensors as far as a quarter mile away from the RAWS, while staff from the Forest Service provided feedback on the data that was being collected and the location of each of the sensors.
At the end of September, the Forest Service signed a contract with Voltree Power to deploy up to five battery-powered sensors at a cost of $24,500. After further testing and evaluation, if the sensors meet the Forest Service’s needs, the agency will put out a competitive bid for the technology.
Plans for the next test of the system are not set, but Henderson said battery-powered sensors will probably be deployed in a prescribed fire in early spring to see how they stand up to fire and smoke.
The tree-powered sensors could be deployed as early as June when Voltree plans to complete testing and finalize the design in time for the completion of an upgrade to the Forest Service IT system that supports RAWS. The tree-powered sensors and upgraded IT system could provide forest monitors with data from up to 40 sensors around a single weather station, Karavas said.
