written by: Matt Schelke•edited by: Lamar Stonecypher•updated:
3/24/2010
Renewable energy comes in many forms: wind, water, wave,
geothermal, etc. But how about tree energy? A new study from MIT
reveals trees have chemical energy potentially producing
electricity.
Experimenting with Tree Energy
When Christopher Love takes a walk in the woods, he finds
giant batteries. These batteries aren't typical Duracells or
Energizers, though. They are tens of meters tall, with
trunks, branches, twigs, and leaves. They are trees.
A recent experiment by Love and his colleagues at MIT
reveals that pH differences between tree trunks and the
surrounding soil create voltage differentials, just like
those found in household
rechargeable batteries. Energy flow across these
differentials can power tiny electrical devices.
According to Love, "it has long been known that there is a
voltage difference between the xylem of many plants and the
surrounding soil, but the mechanism behind this voltage has
remained controversial". The MIT team's paper discusses both
the mechanism (the pH differences) and, more importantly,
the applications of this critical discovery.
Using Energy to Power Sensors
Because the trees can only produce about 200 mV of electricity,
they cannot power large-scale lighting, heating, or industrial
systems. But the trees can power small sensors- sensors that can
save thousands of acres of forested land from deadly wildfires.
Wildfire detection is notoriously tricky. Traditional,
battery-operated sensors are placed high on trees in remote
wilderness. As the batteries need constant replacement, millions
of dollars are spent on sensor network maintenance every year.
Tree-powered sensors could eliminate most of that cost.
In addition, the tree sensors can collect real-time information
on air, soil, and water conditions in remote areas. Ecological
and environmental researchers usually travel to the locations
that they study. The sensors would allow them to collect data
from the safety of a lab. It's the difference between driving
fifty miles on dirt tracks to collect a temperature reading and
having that reading fed into your computer as you lounge in an
armchair at home.
However, the new technology raises some important questions.
Trees are a novel source of
renewable energy, but they are also essential parts of
forest ecosystems. If thousands of trees are "plugged in", will
there be any effect on soil and water conditions? If trees are
used to power remote sensors, how will animals be affected by
the thousands of wires strewn across the forest?
Now, though, tree bioenergy converters (produced by
VoltTree, a subsidiary of a major electronics
manufacturer) are just being developed for fire sensors.
According to Victoria Henderson, VoltTree's devices
"truly have potential". If they work well, the power
units could be used for nationwide infrastructure.
These generators are still in the early stages of
development. Even in the nascent stages, though, they
still represent an extraordinary leap in renewable
energy research. Trees are no longer just
landscaping features and sidewalk liners, but natural
generators bristling, bubbling, and popping with energy.
Sources
Love CJ, Zhang S, Mershin A (2008) Source of Sustained
Voltage Difference between the Xylem of a Potted Ficus
benjamina Tree and Its Soil. PLoS
ONE 3(8): e2963. doi:10.1371/journal.pone.0002963
VoltTree Power. http://voltreepower.com/index.php
Power From Trees.
http://www.alternative-energy-news.info/power-from-trees/
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