GIVING alcohol to gun-toting troops might sound like a recipe for disaster.
But US government researchers reckon this may be what鈥檚 needed to power the
ever-growing arsenal of high-tech gadgets carried by today鈥檚 fighting
forces.
鈥淪oldiers are going to be carrying a lot of electronic gear in the future and
they鈥檒l need something better than batteries to power it,鈥� says Ed Baker of the
Pacific Northwest National Laboratory in Richland, Washington. Baker and his
team say they could run a powerful but portable fuel cell on hydrogen extracted
from alcohol in a miniature conversion unit.
Today鈥檚 batteries are so heavy and run down so quickly that soldiers haven鈥檛
been able to use much of the technology that has been developed for them, says
Baker. This includes laser rangefinders and helmet-mounted display systems. So
the US Department of Defense asked Baker and his group to develop more
lightweight power sources that will also last longer.
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Baker鈥檚 team decided to focus on compact fuel cells. These devices normally
run on hydrogen from pressurised tanks. 鈥淎s well as the difficulty in carrying
it, it鈥檚 a safety hazard,鈥� says Baker.
So Baker and his colleagues developed a miniature fuel processor that
converts methanol鈥攖he simplest alcohol鈥攊nto hydrogen. The hydrogen
can then be fed into a lightweight fuel cell to provide electricity for the
soldier to use, he says.
The system works by reacting methanol and water vapour in tiny chambers at
400 掳C鈥攕ome of the methanol is burnt to provide the heat. At this
temperature, the gases react to produce hydrogen, carbon dioxide and carbon
monoxide.
But there鈥檚 a snag. While CO2 can pass through the fuel cell
harmlessly, carbon monoxide reacts with components in the cell and can cause
permanent damage. 鈥淥ne way or another, you鈥檝e got to get the carbon monoxide out
of there,鈥� says Baker. A possible solution, he says, is to add oxygen to the gas
mixture, so the carbon monoxide oxidises to form CO2.
The PNNL fuel processor is designed to fit within a 5-centimetre cube-shaped
enclosure. When connected to a fuel cell, it should produce 25 watts of
electrical power for two weeks, Baker says. Batteries designed for the same job
would weigh around 10 kilograms, about 10 times the weight of the fuel processor
and cell combined.
During the next year, Baker plans to test the fuel processor and connect it
to a hydrogen fuel cell to check how much power it produces in practice. Eugene
Smotkin, who works on portable power sources at the Illinois Institute of
Technology in Chicago, says Baker鈥檚 toughest job will be stripping out enough
carbon monoxide to keep the fuel cell working efficiently.
But if the system works, it鈥檚 the soldiers who may have to worry, adds
Smotkin. Since the system runs at 400 掳C, troops will be easy to spot with
infrared cameras. 鈥淔or the Department of Defense it鈥檚 a big issue, because if an
object is that hot, you can knock it out with a heat-seeking missile,鈥� he says.
The PNNL team is now working on ways to insulate the system.