Researchers from the California
Institute of Technology, the University of Southern California and Northwestern
University have built a propane-driven fuel cell that's not much bigger
than a watch battery, but lasts much longer.
Two of the fuel cells would have enough power to drive an MP3
player. The devices could also be used to power tiny flying robots, and
to provide power for electronic devices like laptop computers and cameras,
according to the researchers.
Propane packs twice as much energy for its weight as methane,
which is more often used for fuel cells.
The challenge of making a small-scale propane fuel cell work was
figuring out how to get the device to generate enough heat to sustain
the chemical reaction that extracts energy from fuel.
The researchers met the challenge using a catalyst that generates
enough heat to maintain the reaction at 500 to 600 degrees Celsius, and
a heat exchanger to keep the heat within the device. The catalyst is a
porous film of ruthenium metal particles and cerium dioxide. The catalyst
speeds the chemical reaction that extracts energy from propane mixed with
The researchers' prototype consists of a pair of propane fuel
cells positioned back-to-back in a nested pair of quartz tubes that channel
the fuel to and away from the cells. The prototype generates 1.44 volts.
The researchers' prototype requires that it be heated to 300 degrees
Celsius in an oven to jump-start the reaction. The researchers are working
on making the reaction work from a more practical starting temperature.
The technology could be made practical in 5 to 15 years, according
to the researchers. The work appeared in the June 9, 2005 issue of Nature
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