Fuel cells and Cell phones:
A subject previously discussed here.
This will extend the "battery" life exponentially. The wireless revolution is truly just beginning.
Methanol fuel cells seen as mobile phone power source
By Nadya Anscombe
EE Times
(02/08/00, 5:04 p.m. EST)
SCHAUMBURG, Ill. ? Researchers at Los Alamos National Laboratories and Motorola Inc. have designed a liquid
methanol fuel cell with an energy density 10 times greater than conventional rechargeable batteries and which could
potentially be applied to mobile phones. Such phones could be powered by a small methanol reservoir about the size
of an ink-pen cartridge that would last about a week, its developers said.
The fuel cell operates at room temperature and, because it does not use air pumps, heat exchangers or other devices
used by conventional fuel cells, can fit a broad range of portable electronic products.
According to the engineers, a catalyst ? typically a mixture of platinum and ruthenium ? promotes a reaction in a
dilute mixture of methanol and water to form carbon dioxide, protons and electrons. The protons are conducted
through an organic membrane to a second platinum catalyst where they combine with oxygen from the air to form
water. Some of the water is recycled back to mix with the methanol, and the excess is given off as water vapor
together with the carbon dioxide gas. The electrons are available to drive electronics at a potential of about 0.5 V.
Bill Ooms, director of material, device and energy research at Motorola (Schaumburg, Ill.), said that allowing for the
movement of gases in and out of the cell is not a problem for integration into portable devices ? zinc-air batteries in
hearing aids use a similar mechanism, he said.
Ooms said the main challenges with this technology are the catalyst chemistry and the design of the membrane.
Complicated catalyst
Most other fuel cell research has concentrated on hydrogen, but although methanol has the advantage of being a
liquid and has a higher energy density than hydrogen, it needs a more complicated catalyst to function. Advances in
catalysis chemistry, membrane research and circuit design have enabled this advance.
Motorola researchers have designed circuitry that converts the low voltage of the fuel cell to the higher voltages
required to allow the cell to replace conventional batteries and directly drive portable electronics.
"Our prototype uses pulse-width modulation but with external switches to get low losses," said Ooms. "Our novel
circuitry can start up my mobile phone with 0.5 V. We are now planning to develop the ASIC. But don't look in
the shops just yet. Our development plan is three to five years. By then we hope to have an overall methanol
conversion efficiency of 40 percent and small methanol cartridges, like today's ink-pen cartridges, for customers to
refill their mobile devices. Each cartridge would power a mobile phone for around a week."
Nadya Anscombe is technology editor of Electronics Times, EE Times' sister publication in the U.K. |
