Toshiba has unveiled a prototype fuel cell it hopes will become the power source for laptops in the future.
By Mark Ward
BBC News Online technology correspondent
The fuel cell breaks down methanol to generate power and, Toshiba claims,
will provide enough juice to run a laptop for about five hours.
Fuel cells should work with existing laptops
To get the cell working, the alcohol fuel is provided in small 50cc cartridges.
Toshiba hopes to put the fuel cell on sale in early 2004.
Fuel cells which use chemistry to generate electrical power by catalysing
substances such as hydrogen are already being touted as a green power source
for the future, especially for cars and other light vehicles.
Fuel cells for cars typically use hydrogen but, said Toshiba spokesman Yoichi Akashi, the company will
be using methanol in its portable power source.
"Compared to hydrogen, methanol is much safer," he said.
Fuel cells for cars typically have a large tank that holds the fuel in the
best concentration to generate power, said Mr Akashi.
Bolting a large tank on the side of a laptop was impractical so Toshiba
developed a way to re-use the by-products of the fuel conversion process to
maintain its fuel source in the right concentration.
When methanol is broken down it generates carbon dioxide and water. The
water is used to dilute the concentrated methanol held in the fuel cell's
cartridige and keep it at the right concentration.
This means that the laptop fuel cell requires a cartridge with a capacity of
only 50cc, approximately one-tenth of the size it would need if it only
stored methanol in the required 3-6% concentration.
The methanol cartridges are about the size of a computer mouse and the
prototype of the fuel cell is larger - about the size of a house brick.
Toshiba has developed a new material to shrink the stacks where the methanol
is physically broken down. It has also developed sensors to monitor methanol
concentration and liquid level as well as tiny liquid and air pumps to keep
the fuel souce circulating.
Average power output is 12W and maximum is 20W. Unused energy is stored in
the fuel cell.
The methanol cartridges will also be refillable, just like those used in gas
Mr Akashi said the commercial versions will be slightly larger than existing
lithium-ion batteries and use the same power interfaces so they should work
with older laptops.
Existing laptops should get about five hours of work time out of a fuel
cell, said Mr Akashi. Laptops that use Intel's Centrino chipset that
minimise power use should get up to 20% more time.
Future versions of the fuel cell should be able to power a laptop for about
10 hours. Toshiba is also working on fuel cells for PDAs and cellphones.