Wednesday, June 19, 2013

Fuel Cell Challenges

Recent dramatic increases in
the availability of natural gas
will change the way we convert fuel
into energy. Fuel cells are one promising
option; these clean, high-efficiency
devices may challenge the traditional
internal combustion engines used in
today’s cars. Shawn Litster, a professor
in Mechanical Engineering and a 2011
winner of the prestigious National Science Foundation
CAREER award, runs a lab focusing on proton exchange membrane
(PEM) fuel cell systems research.
“A fuel cell is an electrochemical engine,” Litster explains, “We
take hydrogen, plus oxygen from the air, and allow them to react over
two electrodes, or two metal surfaces. They then produce water and
electricity.” Unlike internal combustion engines, fuel cells do not create
harmful emissions; they have no moving parts and are completely
noise-free. Fuel cells also boast the high efficiencies necessary for
vehicular applications. “They can give twice the efficiency of an internal
combustion engine, and they can offer similar distances as an internal
combustion engine, 400 miles,” says Litster.
However, there are challenges to overcome before fuel cells are
a financially viable alternative to traditional devices. “Fuel cells use a
platinum catalyst, which is an expensive metal,” says Litster. Another
issue is the large voltage losses that occur due to oxygen transport
limitations, which hinder the reaction kinetics at the electrode’s catalyst.
Litster and his graduate researchers are trying to understand these conversion
losses at the nano- and micro-scale in order to make fuel cells
more affordable.
Litster’s group, whose members include an Environmental Protection
Agency-STAR fellow and a Department of Energy National Energy
Technology Laboratory intern, among others, has gained recognition
for their micro-structured electrode scaffold (MES) diagnostics, which
allows them to take micro-scale measurements ‘in-situ,’ or during a fuel
cell’s operation. These measurements can say a lot about the performance
of a fuel cell that theoretical modeling currently cannot. “When we do
in-situ measurements we can distinguish what the real limitations are to
reaching the full potential of the device,” Litster says.
Widespread use of fuel cells may not be far off. Companies like
Walmart with large distribution centers are beginning to replace the
batteries on their forklifts with fuel cells. “They might have a whole area
of the center dedicated to charging lead-acid batteries,” Litster says,
“What a fuel cell would do is reduce the number of times they would have
to switch out batteries and eliminate the entire battery charging facility.”
Litster has also worked with Angstrom Power, a Canadian company
that produces miniature fuel cell systems for mobile phones. Fuel cells are
an attractive prospect for handheld devices due to their combined high
power and energy densities. Litster says, “The benefit is that the energy
density requirements at the consumer electronics level are unlimited” as
the device functionality increases with the power source’s capacity. Litster
notes that the BIC Corporation recently acquired Angstrom Power. Perhaps
someday fuel cells will be as ubiquitous as pens or handheld lighters