By Burt Helm A group from the University of Illinois has built the first membrane-free alkaline fuel cell. Announced for the first time on Mar. 22 at the American Physical Society's meeting in Los Angeles, it's a step toward creating an affordable and efficient power source that could increase the battery life of laptop computers and other electronic devices to anywhere between 10 and 40 hours (see BW, 2/21/05, "Laptop Batteries that Last All Day").
Fuel cells, which mix hydrogen compounds with oxygen compounds to create energy, have shown promise as alternative energy sources for everything ranging from cars and trucks to small electronics. "There are different applications all the way from megawatt-producing cells down to 20 to 40 watts," which is about the power needed to run a laptop, says Paul Kenis, an assistant professor of chemical and biomolecular engineering at the University of Illinois and the group's leader.
MEETING, NOT MIXING. Kenis' fuel cell is designed for that low-power end of the spectrum. While high-wattage designs used by NASA's space program break down pure hydrogen and oxygen gas from pressurized canisters, Kenis' group uses two cheaper and considerably less volatile substances -- methanol and highly oxygenated water.
Here's how it works: The fuel cell itself is a Y-shaped channel, with methanol flowing down the left side and water down the right. In a typical fuel cell, there is a membrane separating the hydrogen-based and oxygen-based compounds, which regulates the chemical reaction, and keeps electricity flowing at a steady rate.
But in Kenis' fuel cell, the two liquids meet in the middle as they flow down. What stops the methanol and the oxygen in the water from mixing and reacting all at once? It's a concept called "laminar flow." The center channel is so narrow -- roughly 1 millimeter wide and 1 millimeter higher -- that that each liquid's own surface tension keeps it intact. The result is two tiny streams pushed against one another, without any mixing, "like Aquafresh toothpaste," says Kenis.
BOOTS CLOGS. Eliminating the membrane removes a large component of the total cost. But the particular advantage of this design is that similar to electronics battery cells, it is alkaline -- a more efficient kind of fuel cell than the acidic-type cells most commonly used today. That makes it compatible with the battery cells found in laptops and other electronics.
Manufacturing such compatibility has been difficult in the past, because alkaline reactions often result in carbonate formation, a chalky white byproduct that clogs the membrane of today's cell.
Because Kenis' design takes advantage of a steady liquid flow, he found that as the tiny carbonate particles form, the used-up fuel simply washes the carbonate away, preventing any buildup.
CHANNELING THE POWER. So far, the cell is just proof-of-concept, and technical hurdles remain. The wattage output is not yet strong enough to power a computer. And because the design necessitates that the internal channel be extremely narrow, it will require clever engineering or possibly several channels working in tandem to create enough power. Kenis says his research group is also looking at ways to make the hydrogen and oxygen supplies more potent, so that the breakdown will be more powerful.
The group is currently working with INI Power Systems, a Cary (N.C.) engineering outfit, to commercialize the cells. Kenis estimates that a prototype powerful enough for a laptop will be ready in three years. One more small step for fuel cells could mean a giant leap in laptop battery life very soon. Helm is a reporter for BusinessWeek Online