INDUSTRY TRENDS
Will Fuel Cells
Replace Batteries
in Mobile Devices?
Linda Dailey Paulson
N
o matter how much wireless
vendors improve their processors, memory systems,
and networks, it does no
good if a mobile device’s battery dies or has such a short life that
users are virtually tethered to an electrical outlet. With this in mind,
researchers are seeking to improve
portable-power technology, and many
are exploring a single alternative: fuel
cells.
The nickel-cadmium and lithium-ion
batteries generally used in laptops, cellular phones, PDAs, and other portable
computing and communications devices have increased their energy
capacity by 10 to 15 percent per year,
according to ABI Research analyst
Atakan Ozbek. However, he said, these
technologies are capable of providing
only another 15 to 25 percent.
This won’t keep up with the increasing power demands of mobile devices
spurred by developments such as faster
processors, higher-resolution displays,
and games and other power-intensive
applications. As it is now, laptop and
cellular-phone batteries provide only
three and four hours of use, respectively.
Because of this, universities, corporations, the US Defense Advanced
Research Projects Agency, and several
US national laboratories are sponsoring
and conducting considerable research
on fuel cells for mobile devices.
Japan’s NTT DoCoMo has announced plans to release a fuel-cell-
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powered cellular phone by 2004, indicating the technology may be about
ready for prime time.
However, Ozbek said, whether the
technology is truly viable commercially
remains to be seen. Traditionally, fuel
cells have been too big and expensive
for smaller devices. They also face
other challenges, which researchers are
trying to overcome.
FUEL-CELL PRIMER
Both batteries and fuel cells create
electricity via electrochemical reactions,
explained David Dorheim, CEO of
fuel-cell vendor Neah Power Systems.
The standard battery creates energy
via an electrochemical process involving multiple elements, which vary
depending on the type of battery being
used. The electrochemical process
causes the release of electrons, which
can provide electricity to a host device.
Batteries are sealed, self-contained
energy sources to which new elements
cannot be added. When their elements
produce all the chemical reactions they
can, batteries are useless except for
those that can be recharged, a process
that adds capacity by reversing the
power-producing chemical reaction.
Fuel cells produce energy via a
chemical reaction between oxygen
and either hydrogen or a hydrogencontaining substance such as methanol. Direct-methanol fuel cells
(DMFCs) have become an important
focus of research on fuel cells for
mobile devices.
Electrodes draw the fuel substances
toward a porous membrane. When the
substances contact the membrane, the
hydrogen-containing material breaks
down, releasing electrons that can provide electrical current for a device. The
remaining hydrogen ions combine
with the oxygen to form water as the
process’s principal byproduct. Users
can add more fuel to the cells, which
are generally open systems.
Fuel cells have been used in such systems as furnaces, power-generation
plants, and vehicle engines. However,
they’ve been too big for portable
devices until now, as Figure 1 shows.
FUEL CELLS FOR MOBILE DEVICES
Proponents say fuel cells will offer
mobile devices longer life than batteries. Mobile devices have different
needs than other machines that run on
fuel cells. For example, mobile devices
generally must be small and inexpensive. Researchers are thus working on
micro fuel-cell technology that will
meet these needs while still providing
the devices with more power than they
receive from batteries.
Much of the work focuses on fuel
cells’ polymer membrane, which is
highly conductive, and chemically stable, but expensive, Dorheim explained.
Considerable research is taking
place on proton-exchange-membrane
fuel cells because vendors are familiar
with them and off-the-shelf components are readily available. However,
current PEM fuel cells have been too
large for most mobile devices.
In addition, the membranes work
only under nearly ideal conditions,
which must be maintained with com-
plex control schemes and ancillary
equipment. The membranes can also
experience problems such as tearing,
distortion, or improper fuel migration.
Replacing polymer with silicon
Neah Power Systems has replaced the
typical thin polymer membranes with
stacked, porous silicon layers. This
could improve performance and make
the fuel cells easier to manufacture via
techniques long used for working with
silicon in chips and other products.
In a fuel cell, the number of electrons
produced is directly related to the
membrane’s surface area. Therefore,
increasing power requires expanding
the size of the polymer membrane and
thus the fuel cell itself, a problem for
systems designed for small devices.
However, by stacking porous silicon
layers, Neah has created 40 times more
surface area than a polymer membrane
provides, even though the overall fuel
cell is the same size.
Neah’s fuel cell also obtains the oxygen necessary to feed the chemical
reaction via a 30 percent hydrogen peroxide solution, rather than via air from
the atmosphere, as is typically the case.
According to Dorheim, Neah has created a sealed system in which the
hydrogen peroxide molecules, as they
break down, yield a substance that is
90 percent oxygen and thus very effective in fueling the chemical reaction.
He said air from the atmosphere,
which can contain system-threatening
contaminants and can dry out membranes, is only 20 percent oxygen.
The company is designing its fuel
cells the same size as laptop batteries
while providing power for up to seven
hours. Neah plans to begin shipping
products in 2005.
Diluted methanol DMFCs
Some research on DMFCs is focusing on using diluted methanol, which is
easy and inexpensive to produce.
Typically, though, the amount of water
necessary to dilute the methanol
requires a storage container too big for
mobile devices.
Source: Neah Power Systems
Figure 1. Neah Power Systems has developed a fuel cell (left) as small as the batteries
used in laptop computers.
However, Toshiba has developed a
way to route the water already produced as a by-product of the powergeneration process for use in methanol
dilution. The fuel cell—designed for
laptops, cellular phones, and PDAs—
can thus start with higher concentrations of methanol, permitting smaller
methanol containers more suitable for
small devices. Toshiba also shrunk key
DMFC components such as the transformer, some electrical circuitry, air
and fluid pumps, and the cooling fan.
The DMFCs would use a small,
replaceable fuel cartridge and could
provide laptops with power for up
to five hours, according to Masa
Okumura, the Toshiba Digital Product
Division’s director of worldwide product planning.
The first version of the fuel cell
would measure 275 mm by 75 mm by
40 mm, comparable in size to a 12-cell
laptop battery, said Okumura. The
company is also working on fuel cells
of other sizes.
According to Okumura, Toshiba
hopes to release commercial DMFCs
by 2006.
Smaller membranes
for smaller fuel cells
PolyFuel is working on small DMFC
membranes for fuel cells that are
“light, small, inexpensive, and robust
enough to meet the demanding
requirements of portable power applications,” said company president and
CEO Jim Balcom. And, added Balcom,
they can store more than 10 times as
much energy as an equivalent lithiumion battery.
PolyFuel has already released a small
membrane and expects companies to
begin using it in products within two
to five years.
Boron fuel cells
Millennium Cell has been researching the use of boron as a fuel in its
products and now works with water
and sodium borohydride, which
releases its hydrogen after the device’s
chemical reaction. The company says
using boron is an advantage because it
is plentiful and less flammable than
other fuels.
Millennium plans to release its fuel
cells for mobile devices in 2005.
CHALLENGES
Widespread fuel cell use in mobile
devices faces numerous challenges. For
example, the design of mobile computing and communications devices,
including their power-system interfaces,
must change if the devices are going to
use fuel cells instead of batteries.
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also require components to collect and
handle the process’ electricity and byproducts. These components don’t add
appreciable size to large fuel cells.
However, in small devices, the components can increase the cost and size,
making it harder for fuel cells to compete with batteries.
Researchers need to develop passive
systems in which fuel and other elements can move around without pumps
and other components, said Professor
William H. Smyrl of the University of
Minnesota’s Department of Chemical
Engineering and Materials Science.
Source: ABI Research
Fuel flammability
Figure 2. ABI Research, a market research
firm, predicts skyrocketing growth in the
production of fuel cells for small devices
during the next six years.
Lack of standardization
Unlike batteries, which come in standardized sizes such as AAA and C, fuel
cells lack comparable size-related standards. Researchers have developed
prototypes in a wide range of sizes.
According to Okumura, without size
standardization, device vendors won’t
be able to standardize their design
process, consumers won’t be able to
buy one standard fuel cell for all
brands of the same product, and fuelcell use won’t be widespread.
Cost
Fuel cells can be expensive. For
example, PEM fuel cells’ reactive surface is coated with a noble metal—one
that is chemically inert or inactive,
especially in the presence of oxygen—
such as platinum. Noble metals, which
tend to be expensive, are effective at
initiating the fuel-cell chemical reaction that produces power.
Wilson Chu, spokesperson for
Johnson Matthey, a provider of fuelcell-manufacturing supplies, said
researchers are experimenting with
ways to reduce precious metal concentrations in fuel cells.
Most fuel cells need tiny pumps and
valves for moving air and liquids, and
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One of mobile technology’s key features is that users can take devices with
them when they travel. However, airline or airport regulations could prohibit passengers from carrying devices
that contain fuel cells because methanol
and most of the other fuels they use are
flammable.
“Methanol fuel cartridges are going
through the same basic scrutiny that
butane lighters had to go through in
order to be transported on an airplane,” explained Bernadette Geyer,
the US Fuel Cell Council’s director of
outreach programs.
Geyer’s organization is working with
groups, including Underwriters Laboratory and the US Department of Transportation, on these issues. Last year, the
Department of Transportation ruled
that passengers can take PolyFuel’s
diluted-methanol cells on airplanes.
Donald Sadoway, a Massachusetts
Institute of Technology engineering professor, noted that even though diluted
fuels are touted as relatively benign, “at
some level there is concern.”
with supercapacitors, which offer very
high capacitance in a small package,
generating energy via a static charge
rather than an electrochemical process.
Supercapacitors transfer energy and
recharge faster than batteries. A number of companies, including Intel, are
working to bring supercapacitors to
laptops and other mobile devices. Intel
predicts supercapacitor-enhanced notebooks will hit the market in 2004.
uel cells may be used initially to
recharge mobile devices or as a
backup power source for batteries
because, unlike batteries, today’s fuel
cells can’t provide the large power
bursts some functions and devices need.
Fuel cells tend to be better at providing
steady amounts of current because they
work with fuel that is pumped into the
system at a constant rate.
As Figure 2 shows, ABI predicts that
only 5,000 fuel cells will be sold for use
in mobile devices in 2004, but their
popularity will begin increasing rapidly
until 10 million are on the market by
2009.
ABI’s Ozbek said there have not
been major advances in fuel-cell technology recently, so vendors may not
have products ready for use in mobile
devices until 2005.
According to Mike Rocke, director
of investments for mobile platforms
for Intel Capital, which has invested in
fuel cells for mobile devices, “It’s a
question of how many years [will pass]
between prototype development and
actual commercialized products. It’s a
big race right now.”
Rocke said fuel cells will find their
way into the devices, but adoption will
occur incrementally. ■
F
ALTERNATIVES TO FUEL CELLS
Fuel-cell adoption in mobile devices
could be hurt by developments that
would let users continue to work with
batteries. For example, energy-efficient
chips such as Intel’s Centrino are
designed to extend battery life.
Some companies are looking for
ways to supplement battery power
Linda Dailey Paulson is a freelance
writer based in Ventura, California.
Contact her at ldpaulson@ yahoo.com.
Editor: Lee Garber, Computer, 10662 Los
Vaqueros Circle, PO Box 3014, Los Alamitos,
CA 90720-1314; [email protected]