A new sensor system is under
development that runs on electricity
generated by ordinary trees!
Apparently trees are capable of self-
sustaining a reliable source of
electricity. While a tree may not seem
like much of a powerhouse, the
"trickle charge" can add up, "just like a
dripping faucet can fill a bucket over
time," said Shuguang Zhang, one of
the researchers on the project and
the associate director of MIT's Center
for Biomedical Engineering (CBE).
MIT researchers now believe they can
power a network of sensors
connected directly to trees to perform
a variety of tasks.
Trees could serve as “silent sentinels”
along the nation's borders to detect
potential threats such as smuggled
radioactive materials—with the
sensors powered by the trees
themselves. They could also prevent
forest fires, among other applications,
by sending early reports to the
authorities.
Right now, the U.S . Forest Service says
that manually recharging or replacing
batteries in remote automated
weather stations, which usually have
to be located in hard-to-reach places,
makes things impractical and costly.
The new sensor system would bypass
this problem by tapping into trees as
it’s very own self-sustaining power
supply. Each sensor is equipped with
an off-the- shelf battery that can be
slowly recharged using electricity
generated by the tree itself.
The system produces enough
electricity to allow the temperature
and humidity sensors to wirelessly
transmit signals four times a day, or
immediately if there's a fire. Each
signal hops from one sensor to
another, until it reaches an existing
weather station that beams the data
by satellite to a forestry command
center in Boise, Idaho.
Scientists have long known that trees
can produce extremely small
amounts of electricity. Yet no one
knew exactly how the energy was
produced or how to take advantage of
their capacity to generate power. So,
how does it work?
MIT colleagues recently reported the
answer in the Public Library of Science
ONE. "It' s really a fairly simple
phenomenon: An imbalance in pH
between a tree and the soil it grows
in," said Andreas Mershin, a
postdoctoral associate at the CBE.
To solve the puzzle of where the
voltage comes from, the team had to
test a number of exotic theories using
a slew of experiments that proved,
among other things, that the
electricity was not due to a simple
electrochemical redox reaction (the
type that powers the 'potato batteries'
common in high school science labs,
http:// en.wikipedia.org/ wiki/
Lemon_battery ). The team also ruled
out the source as due to coupling to
underground power lines, radio
waves or other electromagnetic
interference.
Testing of the wireless sensor
network, which is being developed by
Voltree Power (http://
voltreepower.com), is slated to begin
in the spring on a 10-acre plot of land
provided by the Forest Service.
According to first author of the paper,
Christopher J. Love, the bioenergy
harvester battery charger module and
sensors are ready. "We expect that
we'll need to instrument four trees
per acre," he said, noting that the
system is designed for easy
installation by unskilled workers.
"Right now we're finalizing exactly
how the wireless sensor network will
be configured to use the minimum
amount of power," he concluded
www.dailygalaxy.com/my_weblog/2008/10/researchers-say.html
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